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SantaMonica 02-01-2009 09:55 AM

Automatic Continuous Feeder - DIY
Automatic Continuous Feeder - DIY

Part 1 of 5

Here is my solution to the problem of trying to feed continuously. My application was for feeding NPS corals in SW, but this will work for plant ferts, and smaller fish. Here is a pic and vid of the food being sprayed into the display:


Advantages of continuous feeding:

Overall: The ocean generally feeds it's corals continuously (although maybe more at night), so duplicating this allows the corals (and some fish, especially tangs) to eat more like they do in the wild.

Less rotting: When you manually feed once or twice a day, much of the food gets past the fish and corals, and rots in the rocks and sand. When you feed continuously, the fish and corals get most of the food before it settles. So you get to feed the same amount, but the fish and corals get more, and less rots.

Keep pumps running: Many people turn their return pump off while feeding, so that food does not go to the sump. This is not necessary with continuous feeding, since most of the food will be eaten in a few seconds, and thus won't even make it to the overflow. So pumps last longer.

Keep skimmer running: Many people also turn their skimmer off while feeding. Again this is not necessary; food removed by the skimmer is being constantly replaced by the feeder (you may have to feed a little more, however, to make up for it.)

Mandatory for NPS: Non Photo Synthetic corals must have as close to continuous feeding as possible. Some of the more difficult NPS will actually close up if you feed too much at one time; thus, small continuous amounts are the only way to keep them alive.

No forgotten feedings: While not critical to fish, some corals (and certainly NPS) may not open again if you miss too many feedings.

More accurate: Since the feeder is automatic, you know for sure how much you are feeding, and how much you have fed. This makes it easy to compare coral growths (as well as nuisance algae growth) while varying the feeding amounts.

Free time: I thought that I'd miss feeding, but I don't. I still get to watch the feedings (for me, every hour), I just don't have to stand up and do them.

The main requirements of the feeder were:

1. Tiny feeding amounts: As little as 0.1 milliliters at a time. The foods that I'm using (Reed's Phytofeast and Reed's Rotifeast for the NPS corals; Reed's Arctipods for the other corals and for the fish) are very concentrated. Reeds recommends that the foods not be diluted in water; so very very small amounts of the concentrate must be fed each time.

2. Adjustable feeding amounts: In order to experiment with how much can be fed before problems arise (like nuisance algae), it needs to be pushbutton-adjustable. If you are feeding non-concentrated foods like melted mysis cubes (1 cube = 3ml), you could easily adjust it to a higher amount.

3. Adjustable feeding schedule: As short as every few minutes, or as long as every couple of hours. Or just plain continuous.

4. Ability to feed very thick liquids, including melted mysis cubes.

5. Refrigeration: Would keep the liquid chilled at all times, with an adjustable temperature as low as freezing (but would not freeze it).

6. Capacity: Would hold enough to feed an entire month without refilling.

7. Would sit on top of tank, so that the food would go directly into the display. This means the unit would need to be small, quiet, and have a decent appearance.

8. Reliability: It would not fail (and thus not starve the tank.)

9. Mechanically Safe: No possibility, at all, of all the food being fed at once.

10. Electrically safe: Splashed water, condensation, or salt creep would not shock anything, and would not cause failure.

11. Settling: Larger pieces of food should not settle to the bottom of the food container.

12. Cost: This is subjective, but for me the ability to keep NPS corals, and to not have to feed again for an entire month, means that I'd be willing to spend several hundred dollars.

Here is my solution: An electronic wine chiller, connected to an enteral feeding pump, sitting on the top of the tank:

A "digital" or "electronic" wine chiller is a thermoelectric chiller that does not use a compressor; instead it only has a fan. Some models actually have a digital readout, but the one that worked best for me does not. An "enteral" feeding pump is a peristaltic medical pump designed to feed patients who cannot eat; it pumps liquid food directly into the intestine. (Note: An enteral pump is different from an "IV" pump).

Here is the "Wine Bottle Cooler/Warmer", as sold on Ebay:

Sample ebay listing (item=260314363628)

Here is the Zevex EnteraLite Infinity feeding pump, as sold on Ebay:

Sample ebay listing (item=320333085006)

SantaMonica 02-01-2009 09:56 AM

Re: Automatic Continuous Feeder - DIY
Part 2 of 5

Here's how these two devices solved the continuous feeding problem...

(1) Tiny feeding amounts: Since enteral feeding pumps are designed to feed concentrated liquid foods to people, they are already set up to handle small amounts of these types foods. My display is about 100 gal, and my starting point was 0.4 milliliters every dose.

(2) Adjustable feeding amounts: This pump can pump as little as 0.1 ml at a time, and is adjustable by just pushing the up or down buttons. I'm feeding 0.4 ml per dose (about 10 ml per day) in my 100gal. A 10 gal nano could get about the same concentration of food by feeding 0.1 ml every 2 hours. As corals or fish are added/removed, or as filtering varies, you can adjust the feeding amount so that nitrate, phosphate and nuisance algae don't get out of control.

(3) Adjustable feeding schedule: This pump can feed as often as every 60 seconds. However, if I did this, I think the fish would hang out at the feeding tube and eat everything that came out. So I feed every hour; this way the fish can't get all the food, and it makes it to the corals.

(4) Thick liquids: Although you are not supposed to mix the Reed's products together for any length of time, it is a concession I had to make (otherwise I'd need three separate feeders). So, with all three mixed (I'm using one part phyto, one part rotifers, and four parts pods), it's a medium-thickness liquid, similar to coffee creamer. But if I wanted to add mysis, the pump would have no trouble with it (and the mysis would fit easily in the tubing.)

(5) Refrigeration: This was a tough one. Like other people, I first thought about a dormitory fridge, but that would be difficult to set on top of the tank. And you don't want a lot of distance between the fridge and the tank, because the food will be sitting at room temp (actually higher when it gets near the lights.) So the wine chiller works perfect. The distance of tubing from the chiller, through the pump, and into the water, is 24" (60cm) (although this could be shortened with creative placement and splicing). At my current rate of 0.4 ml/dose, the food moves 2.5" (63mm) per hour, thus staying at room temperature for 9.6 hours. Seems to be an acceptable time for my first attempt. Less is better, of course, because it's less nitrate and phosphate that bacteria will cause.

(6) High capacity: This was an easy add-on feature, since everything is already in place. The Zevex pump uses 500 or 1000 ml bags; the 500 bag fits right into the chiller, but not if you fill the bag all the way up. 120 ml (12 days of food at 10 ml/day) is no problem, however, with plenty of space. I'll be trying more soon.

(7) Top of Tank: When turned sideways, the chiller is only 6" (15cm) wide, and fits easily behind my light. And the pump can be laid flat, or stood up, or attached to the chiller (or pole, or bracket) with the included screw-on bracket. This allows the food to be released right in front of a powerhead, which sprays the food all over the corals/display.

(8) Reliability: The pump was designed for battery operation, and sure enough I've gone well over one month of operation without charging it. (Most medical patients use much more food than we do, so the time between battery charges is much much longer.) And if the bag runs out of food, a beeper lets you know.

(9) Mechanically Safe: The last thing you want is for a month's supply of food to be dumped in at once. Being a medical device that keeps people alive, there is very little chance of this pump failing in that fashion. And if the bag were to ever leak or break, it's inside the chiller (which you seal with silicone at the bottom), so the food would just sit there and stay cold.

(10) Electrically Safe: The pump is completely sealed; not just water resistant, but waterproof. The instructions actually say to wash the pump by pouring water on it. Salt creep or splashing is a non-issue. Electronically, there is no way for the pump to stick "on" and accidentally dump the whole bag. There are all sorts of safety features that would stop this from happening. The chiller is powered by just 12V (the transformer is a long ways away). While it would be possible to splash water on the chiller and short it out, it should not harm anyone/anything. If the chiller did fail, the food would still be fed to the tank, but it would just slowly start getting warmer over the next few hours.

(11) Settling: If you were to have a large container with thin and thick foods mixed together, the thick food (like mysis) would settle to the bottom and either not get used, or get used first. The feeding bags used by the pump, however, can be twisted and rolled up, thus making many small places for the bigger food to stay.

(12) Cost: The chiller is easy; mine was $20 USD (new in box) from Ebay; just add shipping. The pump is a different story. I monitored Ebay for two months, and saw these pumps sell for as little as $130 used, or up to $600 new. (They are $1500 retail). Plan to spend some time in your Ebay search, checking each day for a new listing. I paid $300 for mine, and $350 for another one. Another "ebay" site, for medical items, is Just search for "zevex". In any case, make sure you get the blue Infinity, NOT the orange one. The orange one will not work.

Pump details:

Here's why you need to stick to this model chiller: All wine chillers will cool a bottle of wine, but the big differences are:

Will it cool to freezing? Some units will only cool to 25 or 30 degrees (F) below the room temp. The room temp near the lights could be 100 degrees, and thus, 70 degrees is too hot for the food. This unit can chill to freezing while it's right next to the lights.

Is the inside compartment waterproof? There will be constant condensation, melting ice, and the possibility of a broken bag. This model is almost waterproof the way it comes; with one application of silicon along the bottom seam, it is totally sealed.

Does it connect to 12V or 120V? You don't want 120V leading all the way up to the chiller. Instead you want the 120V to go to a converter/transformer (like with a laptop), and then have the low voltage wire run up to the chiller. This model works this way.

Will it continue to run if not touched? Many models are designed to turn off after a few hours. This model stays on constantly.

SantaMonica 02-01-2009 09:56 AM

Re: Automatic Continuous Feeder - DIY
Part 3 of 5

Here's why you need to stick to this model pump: There are hundreds of medical pumps on Ebay. You WILL be tempted to get a cheaper one (I got two cheapies, one for just $25! Was a complete waste of time.). Here's why you want to pay the extra money and stick to this Zevex model:

Small Dosages: This is the important one, and you probably won't find out until you get the wrong pump in your hands (I didn't). Most enteral and IV pumps are 1.0 ml minimum. This means that the smallest amount it will pump at one time is 1.0 ml. That's a LOT of concentrated food! (One mysis cube is 3 ml.) I'm currently dosing 10 ml/day. If I had to dose 1.0 ml at a time, I'd have to wait to dose about every two hours. And a 10g nano could only dose this once a day. So having a 0.1 ml capability opens up an entire world of feeding. The other advantage of small dosages is that you can dose even more often than once per hour. I could dose 0.1 ml every 15 minutes, and still end up with 10 ml/day.

Interval Feeding: This is the other important one. Many pumps don't have this option (and they don't list this info on Ebay, so you won't know); instead they dose a constant amount, all the time. If you dosed constantly, your most aggressive fish would hang out at the tubing and eat everything before the other fish and corals got anything. You need to burst out all the food at one, every so often. Of course, a coral-only tank is different, and fortunately the Zevex pump does continuous pumping also.

Not for IV use: IV pumps are those huge ten or twenty pound contraptions that are mounted on a pole in hospital rooms. They are very complex, and many of them have computer connections. And they are very expensive. The only way to get one under a few hundred dollars is to get one from the 1990's, but then it becomes impossible to finds the "drip sets" (or "cassettes") that you MUST have for it to work. I bought two of them, and could get neither to work without the cassettes.

Small Size: IV pumps are just too big to set on top of a tank. Even some enteral pumps are too big. But this Zevex model is probably the very smallest there is of ANY pump. And certainly the thinnest. Most pump pics on Ebay don't show or tell you how deep the pumps are. They look small, but when you get it, it's 9" or 12" deep. The Zevex is just 2" (5cm), including the tubing cover.

Waterproof: Very few pumps of any type are waterproof; they were made for the hospital room, not for walking around outside. But this Zevex pump, if operating on batteries, would actually work underwater if you dropped it in your tank.

Current Model: This model is NEW, and is CURRENTLY (January 2009) being manufactured (it just won the product of the year award for medical feeding devices.) This means that you will be able to get the feeding bags ("delivery sets", "pump sets") for many years. A delivery set (usually with a feeding back attached) is required to run the pump, since the pump detects that the proper set is installed. Delivery sets are cheap to buy, but impossible to DIY.

Looks Nice: I think this pump is the best looking of all of them. You won't see it very much on top of a larger tank, but on a nano it would be very noticeable.

Easy to Use: After reading the instruction book, you can set the options up in about 10 seconds. Adjustments like dosage and interval take about a second to adjust. It's an amazingly well built pump; I really think it's worth the $1500 retail.

Note: Some folks have experimented with syringe pumps. But syringe pumps are very large, not battery operated, and unless you get the expensive "retracting" models, then you have to take the syringe out and retract the plunger each time it bottoms out. Plus I'm sure these pumps are not waterproof. After looking at syringe pumps long and hard, I finally gave up and kept searching until I found the Zevex pump. I can see why continuous feeding has had a rough start until now.

Important: (1) Make absolutely sure you get the AC adapter with the pump. The adapter uses a proprietary waterproof connector to the side of the pump. You cannot use any other type of adapter, and you cannot buy this adapter anywhere else. (2) Get several "delivery sets" (also called "feeding bags" or "pump sets"). You have to replace them every so often; see recommendation further below. (3) Ebay requires the seller of medical devices to say something like "you must be a licensed medical professional to buy this product"; but don't worry, they never actually ask.

Pump operation:

AC power connector for charging battery (does not need to be connected to operate):

Open the cover:

The "delivery set" or "pump set", which is the blue flexible silicone tube, is stretched over the big black wheel to the left:


Close cover:

Cut the tubing so that it barely reaches into your tank water:

SantaMonica 02-01-2009 09:57 AM

Re: Automatic Continuous Feeder - DIY
Part 4 of 5

Now for the settings. Think of this pump as putting sugar into coffee, using a spoon. The size of the spoon is the "dose"; the time between spoons is the "interval"; and how fast you pour the spoon in is the "rate". We only care about adjusting the size of the spoon (dose), and how much time between spoons (interval). We do not care how fast we pour the spoon in, so it might at well be as fast as possible so the fish don't hang out at the pipe and eat it all.

Set how much you want dosed each time; I started by setting it to 0.4 ml:

Set how often (interval) you want it to dose; I started with once per hour:

Set the rate; Max is 600 ml/hr:

Now mix your food ahead of time; I started by using 1 part phyto, 1 part rotifers, and 4 parts pods:

Mix together and pour it into the bag:

Get as much air out of the bag as you can before you put the cap on. Then, turn it over and use the "prime" button to pull the remaining air out (might take a while.) The less air in the bag, the less bacteria will cause nitrate and phosphate to develop:

Now you are ready to fold the bag and put it into the chiller. This is 120 ml of food in the 500 ml bag (it could hold a lot more):

Fold the side with the tubing first, so that it stays on the inside (which helps keep it from freezing.) Don't fold it "tight" or you will cut off the flow. Just curve it around. If you get a "No Flow In" warning after running it, it's either because you folded this too tight, or something has started to freeze:

Next fold the other side; the idea here is to surround the tubing to keep it from touching the metal wall of the chiller:

A very thin towel (or a small filtersock), lining the metal chiller wall, will keep the bag from touching it and will help keep it from freezing (this is only needed if you keep the thermostat set to full cooling):

SantaMonica 02-01-2009 09:58 AM

Re: Automatic Continuous Feeder - DIY
Part 5 of 5

Insert the bag into the chiller/towel, but be very careful to not bind the tubing where it connects to the bag at the bottom, and also keep the tubing in the middle as it leaves the chiller; you don't want it getting near the heat outlets on the sides of the chiller:

Now fold down the cap of the bag into the chiller:

Fold the remaining towel (if used) over the top, or if you used a filtersock, cover it. You'll have to experiment with how much towel to use, and how tight, so that it does not freeze:

Instead of a towel, you may try inserting a small filtersock:

Covering the filtersock loosely will keep the food less cold:

Covering the filtersock tightly will keep the food more cold:

Lastly, use the "prime" button again to bring the food all the way to the end of the tubing, and then push "run". It will begin by pumping one dose, and then the timer will wait for the next one. At anytime, you can push the "vol/total" button and it will display how many ml has been fed since you pressed "run":

To make any pump adjustments, push the "run/pause" button first (which pauses it), and then make your changes. You can reset the "total amount fed" to zero by pushing the "clear" button when it is displaying. You can turn the unit off while it's running or paused; when you turn it back on, it will be in the same state (run or paused) that is was in when turned off. And it remembers all settings, including total amount fed, even it you unplug the AC adapter.

Things to watch out for:

Bag positioning if noise is a concern: The chiller has a thermostat, but the annoying thing about it is that it clicks every 30 seconds or so as it adjusts temperature. If it's in your basement, then it's no problem. But if it sits on the tank like mine does, or if it's in your bedroom, then you don't want this clicking. The way to eliminate it is to put the temperature selector on the coldest setting. This causes the thermostat to always stay "cooling". This fixes the clicking. However the temperature can get very cold after a day or so, and if you seal the top of the chiller with a towel, then the food will eventually freeze. To prevent this, leave the top of the chiller loosely open, and don't push the bag in down to the bottom. Use a towel, loosely wrapped around the bag, to keep the bag from touching the metal walls or bottom of the chiller. This works; it won't freeze. But if you wrap it too much, then the food will not stay cold enough. So this is certainly one area where experimenting will help. Of course if you don't mind the clicking, the thermostat will keep the food perfectly at just above freezing for you.

Frozen spots: If you are using the "quiet" option where the chiller stays running constantly (no thermostat clicking), keep a close eye on the parts of the bag that touch the metal walls. If it's going to freeze, it will probably take 24 hours, or maybe even 48. So check it the next few days by pulling the bag out and squeezing/mixing it all around, especially the bottom where it connect to the tubing. If any part is frozen, then use paper or a towel to keep the bag away from the wall. Also, you could pull the bag up a little, so it gets more air. A good idea is to wrap the bag around the tubing, before you slide the bag in. You might also put a thermometer in with the bag, which sticks out the top, so you can see it while it's running.

Tube near heat: Watch where the tubing goes when it leaves the chiller and heads to the pump. Hot air exits the chiller on both sides, so you want to route the tubing along the back part. Avoid strong lights too.

Charger for pump: You don't need the AC charger to operate the pump, but you do need to plug it in once a month or so, for six hours, to charge it back up. So make sure you can get the charger cable to the pump, without having to move the pump. Of course, you could also just run the pump with the adapter connected, but that's one more cable going to the top of the tank.

Power failures: If the power goes off, nothing happens to the pump; it keeps working on its batteries. The chiller however will stop. But the important point is that this model chiller, when the power comes back on, will switch to full-cooling (no thermostat). This is fine if you were previously running full-cooling, but if you had a temperature set (because you did not mind the clicking), the food will freeze when the power comes back on. For this reason I really recommend the full-cooling setting to be used all the time.

Tube in display water: You want the tube to go into the tank water, so that it does not dry out. If kept above the water, food slowly starts drying out at the tip, slowly clogging it, and causing it to start spraying sideways.

First attempts: I recommend trying it first in your sink, using just water in the bag. Do everything including putting it into the chiller, and letting it run for a few hours. If ok, then fill with food and start it. This first time, and anytime you make changes to the bag, try not to do it right before you go to bed, because if you folded the bag too tight, or if it freezes, the "No Flow In" alarm will sound and wake you up. Better to do it in the morning.

Settings: When first trying to set the settings, it may sometimes not want to accept the numbers you try to set. This is because you have selected a dosing combination that is not possible. For example, if you accidentally set the rate to 0.1 ml per hr (instead of 600), and set the dose to 0.2 ml, and then set the interval to 1 hour, it won't accept it because if you dose 0.2 ml every hour, that is more food than the 0.1 that you set the rate for. Keep the rate at 600 and you should not get stuck as much.

Tubing replacement: The tubing "sets", according to the operating manual, are designed for 24 hours of use at 125 ml/hr. This is a total of 3 liters that the tubing would flow, before it starts to "wear out". Since I'm only pumping 0.4 ml/hr (.0004 L/hr), it would take 7500 hours, or 312 days, before the "wearing out" started to occur. And I'm sure the manufacturer is being conservative since someone's life is on the line. So 6 months (180 days) would seem to be a good replacement time at 0.4 ml/hr. If you were pumping 0.8 ml/hr, you would replace every 90 days, etc.

Proper pump model: Make SURE you get the Zevex EnteraLite Infinity blue pump. There are other EnteraLite pumps which are not Infinity, and they WON'T work. And there is another Infinity which is orange and not blue; it WON'T work.


Several things could be improved with more tinkering or more money:

Separate units: Reeds Foods recommends not mixing food unless just before feeding. This would be accomplished with the (expensive) addition of a chiller/pump unit for each type of food you feed (I use three).

Temperature alarm: Would tell you if the bag gets too warm, or if it starts to freeze. I imagine a freezer alarm would work.

Shorter tubing: The length of tubing from the chiller to the pump could be reduced by 6" or so, if you cut it and spliced it with a connector. You'd need to test it though, to make sure the food you are using can get through the connector. Mysis might be a problem.

Mixing: Although the crinkled and rolled bag will keep much of the food from sinking to the bottom, somebody should find a small, cheap paddle or servo that will shake or vibrate the bag every so often.

Fan quietening: The chiller uses a computer fan that runs all the time. On larger tanks the sound is not noticeable, but on smaller or quieter tanks, or tanks in your bedroom, the fan could be made slower/quieter by inserting a resister into the power lead of the fan. The chiller is powerful and freezes as is; less chilling won't hurt anything. You'll have to experiment with the resistor size.

Food types: With some experimentation, you could mix some solid foods (crushed flakes, tiny pellets, etc) into liquid foods, and maybe even add some type of thickener to it, to keep the solids suspended. Krill is too big for the tubing, but large mysis or small ghost shrimp should fit. Always test it first.

Related Information:

If you are have nitrate, phosphate, or nuisance algae problems, especially when dosing concentrated foods, you may find my other thread on Algae Scrubbers useful:

Article recommending continuous feeding:

Zevex Pump Manufacturer:

Ebay for medical devices (search for "zevex"):

Zevex operating manual:

One of the U.S. distributors of the chiller:

Chiller operating manual:

Zapins 02-01-2009 02:23 PM

Re: Automatic Continuous Feeder - DIY
Wow what a great and thorough thread!

I just wish peristaltic pumps were cheaper. There are so many applications for the with fish tanks, but at $325+ per pump, its not likely that I'll be getting them anytime soon :`(

SantaMonica 02-01-2009 07:44 PM

Re: Automatic Continuous Feeder - DIY
Well some get taken for under $150 (USD). Just depends how good you are with ebay :)

dj2606 02-01-2009 09:08 PM

Re: Automatic Continuous Feeder - DIY

SantaMonica 02-01-2009 09:34 PM

Re: Automatic Continuous Feeder - DIY
That's a good setup for dosing 10 or more ml at a time, which may work great for fert's that are not concentrated. But you could not do it very often, much less continuous.

dj2606 02-01-2009 09:45 PM

Re: Automatic Continuous Feeder - DIY
PPS Pro dosing regimen requires one dose of trace and macro's 1 hour before lights come on.

And each 10ml contains your required dose per day.

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