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.
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 DotMed.com. Just search for "zevex". In any case, make sure you get the blue Infinity, NOT the orange one. The orange one will not work.
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.