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Help with my 75 gal tank

5997 Views 20 Replies 8 Participants Last post by  plantbrain
I have two tanks I would like some help with. I will explain the first now and if things go well will talk about the second one later. This first one is a seventy-five gallon tank. I have about 1.5 inches of soil/sand under about 1.5 inches gravel in this tank. This setup is about six months old.

Lighting: I have (6) 40W NO 48 inch tubes in a suspended hood I built. No metal reflectors, just flat white painted plywood. The tubes are 2325 lumens each, cri-84, 6500K Philips daylight deluxe Altos. The bottom of the tubes are 9.5 inches from the water, and I do not presently have a glass top on this tank.

Ferts: I presently use 10 ppm NO3 from KNO4, 1 ppm PO4 from KH2PO4, .2 ppm Fe from Flourish, and .2 ppm Fe from CSM+B, all twice per week with one 50 to 80 % weekly water change. I have 4 Siamese algae eaters, and about eight 1.5 inch long sheepshead minnows (local).

CO2: My pH is about 6.7 to 6.8. kH seems to be about 5.5 to 6.5. GH I think is about 20.
I get some green algae of the front glass and a little on some of the plants. The algae shows up more on the lighter green leaves. Plant growth is slow to moderate. I just cleamed the glass of the algae before the picture. The water is slightly green. I also have a slight biofilm on the surface that will not go away.

I must be doing something right as there is much less algae in this tank as is in my 125 tank. However, I would prefer less algae and a little more growth. What I think is Rotala indica is a bit scrawny, and growth of the crypts is extremely slow. I figured I was planting too heavily causing less light at the bottom so I have thinned out the plants a bit to get more light down below. I may have reduced the bioload too much as the algae is increasing. Before I had reduced the bioload the B. carolina , L. repens, and Cabomba grew quickly near the top of the tank but were shading the bottom areas too much. Part of my problem is aquascaping. I don't know yet how to grow enough of the tall plants without overdoing it and shading the low plants. My goal is a clear tank with little algae. The darker becketti looks pretty algae free and has been in the tank 6 months, but the lighter quick growing ludwigia has a lot of algae visible on the middle and lower leaves.

One of my problems is that the lighting is not the "standard bulbs resting on the glass top" arrangement, so I have never really figured out how high to hang the lights. I therefore do not know if the tank is a high light or low light tank. It always appears dimly lit to me. I don't want to go with a high light tank if less light will do. I have enough problems with deciding how much to dose anyway. It seems every time I reduce ferts or forget to fertilize the algae increases. So I have been hesitant to lower the lights for more intensity.

Any help on dosing and lighting and algae reduction is appreciated.

Steve Pituch
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Three issues ...

1. Light intensity decreases with distance significantly. Your distance of 9.5" is causing a huge loss of light, at least a half. Not now, but once you get the little algae under control, lowering the hood will help greatly.

2. Too much Fe/TE

3. Your GH is 20, that's a lot of Ca. What is your Magnesium? I can predict none or too low to balance the Ca level. This is why your plants don't grow fast enough.

I would discontinue dosing Fe/TE until deficiency symptoms appear and start dosing the same ppm amount of Magnesium as NO3. In your case 10 ppm.


You definitely are not maintaining a high light system. Although your 6 40 watt tubes may come out to 3.2 wpg, the lack of efficient reflectors and hanging of the lighting 9.5 inches from the surface really cuts back down on light.

Your plants need more light, if the bottoms of those plant species are melting away at that planting density. I would address this issue first.

I would raise the CO2 level to 30 ppm.

As a moderately lit system, I believe you are overloading the aquarium with unnecessary fertilizers. The tank is simply not capable of absorbing all that plant food, and most of it is going down the drain at each water change. I would cut back on how much you dose by half, but do it gradually. Let the tank adjust.

Would you be able to dose for consistency? The algae you describe are, IME, signs of instability. I would split it from two times a week to four times a week.

Let us know how it all works out in the end,

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I agree that you have a moderately lit or even low-light tank despite the 3+ watts/gallon. You can either change things to get more light in the tank or start treating the tank like a low light tank.

Three things come to mind for increasing the light; 1) lower the fixture, 2) build a "wall" around the top of the tank to reflect light back into the tank and 3) convert the light fixture to use t8 lamps.

I can understant why you wouldn't want to lower the lights or build the "wall". Both moves would damage the open-topped aspect of the tank. It looks to me like the lights in your fixture now are about shoulder-to-shoulder, which means that most of the light from the top half of the lamps is restriking the lamps instead of going down to the water. The light you get going downward may be as little as half of the light that the lamps are producing. A big part of the light that does go down is spilling outside the tank. The rest is being converted to waste heat. T8 lamps will give you about 1/2" more space between lamps where light from the top of the lamps can be reflected down to the water. There will also be less waste heat from the ballast and less waste from the fixture.

Carlos' comments on over-running the demands of the tank are about right. I recently decided that CO2 and fertilizer on two low and moderately lit tanks was doing more harm than good. I stopped treating them like high-light tanks; algae is hugely reduced, no plants were lost, plants are growing well and the tanks are both more pleasant to look at and easier to care for. I made the change in three steps First I shut off the CO2, then I stopped macro fertilizers, then I stopped trace fertilizers. I'm in the process now of returning some of the fertilizers to a level appropriate for the tank. First I found (and it didn't take long) that I needed to go back to trace fertilizers. Now it looks like I'll need to add some potassium, which I will do as KCl

Roger Miller
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Edward, Carlos and Roger,

Guys, thanks for your detailed comments. I think you have changed my perspective on this tank. Yes it seems it is quite bright above the lamps due to restrike. Since the soil substrate seems to be working well and I do have a fish load I will try eliminating the co2, macros and traces. I am also not that gung-ho on the open top concept for this tank and may put the glass covers back on too, but then I'll have to lower the lamps a bit more to compensate. I would like to make this a crypt tank so maybe things will work out.

I will post progress as soon as I see it. Thanks again.

Steve Pituch
Here is a progress report.

I have left the lights the same on the 75 gallon tank but have stopped the co2 and nutrients. With the soil substrate and fish load I think I will try this tank ala Walstad.

My 125 gallon tank was undergoing even more serious algae problems. I had previously adjusted the light heights on this tank so the intensity at the bottom was the same as the 75 gallon tank. So it was really a lo light tank also.

What I have done on the 125 gallon tank is to radically lower the lights (2xMH 175W + 96W PC). I think it can be considered a hi light tank now. I am continuing the co2, but for the time being I've reduced the nutrients to 5 ppm no3, .2 ppm Fe, .2 ppm po4 twice per week. I've also cleaned up the bottom and bleached a lot of the plants.

Here is a comparison of the light intensities now:

Steve Pituch
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Get some plants in these tanks!
That's some skimpy planting!

More plants=> less algae, ala Walstad or not.
Add floaters etc.

What is .2ppm of FE?

I add ml of a trace at a known concentration, I assume this is based off an estimation and not a test kit?

The 125 has soil substrate also?
These are often messy and problematic at higher lighting.

I used less than what you have, about 1/2 as much and had more sand cap, 3-4".

I think both tanks would do better with peat/mulm and a turface or Flourite etc type sub.

Get some plants in there though.
Crank the CO2, keep the KNO3 up.
Tom Barr
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The 125 gallon tank has an old Schultz Aquatic plant soil substrate with a lot of mulm. I was adding 10 ppm NO3 from kno3, 1 ppm po4 from KH2PO4, .2 ppm Fe from CSM+B, and .2 ppm Fe from Flourish, twice per week with 80% water changes. Co2 was high, but the light apparently was rather low and considered low light. The 175W MH pendants were about 16 inches from the water. Now they are about 6 inches from the wter. The green algae on the glass, and the brown algae and black beard algae on the lower leaves suddenly got really bad. I also had a very heavy scum on the surface. At this point in time the water temperature in the tank had risen from about 72degF during the winter to about 82degF now in the summer. I am now running a window AC unit to help lower the temps.

This tank was very heavily planted, but to try to get more light to the bottom of the tank I culled out about half the plants. I will add many more plants. I would like to run this as a higher light tank and therefore have lowered the lights. I guess I have to wait for the plants to start using the nutrients.

Steve Pituch
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Steve, for surface scum, a couple of Black Mollies will clean that up in a hurry.
I don't understand why you don't bring the lighting down to where you are using more of it than you are in the NO tank. BTW, a gloss white paint, while not as effective as polished metal, is not a bad reflector.
If you've got the light, use it.
Stuff it with plants. Build a heavy plant mass and after getting a handle on balance, you can always slowly exchange nutrient hogs for plants(Crypts.) more to your liking.
Get the CO2 back up to 30ppm. Get the N and P levels up to 15ppm and 1.0 - 1.5ppm. Dosing extra Fe, especially without the plant mass has always spelled problems for me.
I went through similar issues, scaled down a bit, in one of my 55s with 4-
40watt NOs, and after trying this and that, I just decided to load it up and build plant mass, and fertilize to spec. It's working for me.

Well in both tanks I had everything but the light it seems. 40 ppm CO2, 20 ppm KNo3, 2 ppm PO4 per week. I don't mind having one lo light tank and the 75 has the soil substrate. It will be harder getting a balance in the 125 with the additional lighting. Now I just have to get the plant mass back again. As I said I foolishly cut back on the plants thinking I was blocking the light with them, as the tank looked even darker with the heavy plant load. Time will tell.

One thing I learned(but there was more than one thing) in the 55 I described above, is that I should never heavily prune out more than 1/3 of the tank at a time. It took me 2 years to find the balance for that tank and 20 mins. to screw it up with a pair of scissors.
My 'jungle' tanks all look great......the ones with less than adequate plant mass for the lighting/fishload etc., are a struggle.

These tanks look rather anemic for how rich your nutrient mix is. Without looking at your stats my first impression is low CO2. Yet you seem to supplement more than enough. How are your plant's respiratory cycles?

Do your plants pearl? Do your crypts stream bubbles? How soon do they start each day?

You seem to have a tendency to plant single stems and then let them grow up to lay over the surface. Have you tried trimming short to grow denser stands from the stumps of your stems? If you use frequent pruning to avoid laying over you will also avoid excessive shading. Both R. indica and L. repens respond very well to radical pruning and in my opinion look their best if they don't layover.

I see your canister intake tubes but wonder about your water returns. I found that some surface movement helps to reduce surface scum. My spray bars are placed about 1 inch below the surface and provide nice surface movement with significant top to bottom turn over.

My KH is about 6.5 and I try to keep the pH around 6.8. However it has been going down to about 6.6 in the 125 gallon tank and I have had quite a few fish jump out lately. At the end of the 10 hour light period I have read the pH at about 6.9. I'm thinking that the co2 is about as high as I can safely go. The plants pearl a little but I get a lot of streaming. One thing that I have never noticed is a reductionin NO3. It doesn't seem to get used. I am hoping with more light this will change.

Yes, I think part of my problem is aquascaping. I have had bushels of vegetation growing out of the tank and not enough light at the bottom, I have had a good amount of growth but did not trim them so they floated and blocked light, and I have trimmed out half the plants hoping to get more light at the bottom; all bad things to do to a tank.

I am slowly learning. I have added a lot of stem plants and water sprite. I have started to trim the older ludwigia, bacopa carolina, cabomba stems since they are pretty thickly covered in brown algae at their bottoms. I don't want to do this too fast as I need as much biomass as possible. I added a ton of B. monneri I had been growing emersed.

I am getting green algae on the glass about every two days so I have been cleaning the tank about every three days and doing a 90% water change and readding the nutrients, cleaning out algae on the plants and vacuuming the gravel. I also have my home made UV machine connected to see if it will do anything.

I think that my problem has been light. The two 175W MH pendants now are 5.5 inches above the water, which is what I've seen with other aquascaped tanks. The quality of light looks more like I see with other's nice aquascapes. I also added one 96W AHS light at the center about 4.5 inches off of the water. I don't own glass covers for this tank. I would like to get 4 96W AHS lights for this tank but need to wait.

But now I need to balance trimming the algae infested plants with keeping as much plant load as possible. The tank seems to be doing better.

I appreciate the help.

Steve Pituch
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Seems that gardening these tank well will help you a great deal.
Also, note what it is that you do that causes the tanks to pearl vigorously.

Generally after a water change you can add the nutrients back and see this occur. After a few days, this willd decline.

If you add the right amount of nutrients, this trend will not slow down.
I do not care for CMS personally.

I'd not worry much at all about the NO3 levels. These can be linked to test kit errors very often unless you have a good Lamott kit etc. Even then it's tough to measure 1-2ppm differences in NO3.

I do not think you are far off.

For the 75 gal try this:
Trim and prune, remove mulm, clean filter etc etc. Do this first. Then do the water change routine.

1/2 teaspoon of KNO3 every other day.
Try Flourish only, 10-15mls every other day
KH2PO4- 1/16th to 1/8th teaspoon every other day.

Add macro's on the day of the water and continue every other day.
For traces, add the following day and continued routine.
If your GH is low or lacking in Mg etc, try some SeaChem Eq on the water change day, 1/2-3/4 teaspoon.

The rest should be CO2 issues.
You can improve the tank's growth further by using flourite/onyx in place of sand/soil mixes. Besides these issues, I think the rest is just some time and work on your part.

Generally I never have surface scum accumulate unless there is something not quite right in the tank.

Tom Barr
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plantbrain said:
Generally I never have surface scum accumulate unless there is something not quite right in the tank.
Tom, I think I've noticed this too, but I have a hard time figuring out just what is causing the scum. What sort of problems do you see that cause scum on the surface?

Roger Miller
I followed Tom's suggested doses on my 75gal. incl. Seachem Equilibrium and HCO3 per water change. Also dose micros 3x/wk but I upped my KNO3 to 3/4tsp and it seems to have helped w. the green colored plants. I was using 1/8tsp Mono PO4, but incr. to 3/16tsp to see if a higher PO4 will help with my not so red L.Reopens, A.Reineckii and even R. Nanjenshan.
I also dose 10ml of CSM-B and 5ml's or Flourish 3x/wk too.But overall, the tank looks awesome. I can't believe how healthy everything is! Threw away my Seachem tests as they werent accurate.
Now prune often and toss anything that is sub par, remove all the algae, sickly pieces, keep things clean and trimmed. Replace faster growers with slower growers etc but maintain some fast growers. Just do the work and gardening and things will grow along well.
Stay ahead of things now.

Tom Barr
plantbrain said:
note what it is that you do that causes the tanks to pearl vigorously.
This production of O2 is one of the best ways of observing a tank's daily momentum. A hole in a plant that is the source of a bubble stream will last for several days or even weeks. These holes will put out the same size bubble day after day but their rates will change with photosythetic activity. In the morning a hole may provide bubbles spaced 2 inches apart yet by late afternoon the same hole will have bubbles 1/8 inch apart. I believe this change is an accurate indicator of plant momentum. In general I look for my strongest streams to start about 20 min after the lights turn on and then watch for a maximum rate about 5 hours later which is then steady for anouther 4 hours.

Although intense streams can be encouraged with nutrient supplementation, it is important to supplement to a momentum that can be maintained from one day to the next. Over driving the momentum may provide short term gains but also often encourages deficiency problems. By watching the pearling momentum of your tank you should be able to learn how to gage your rates of plant growth. As you become accustomed to anticipating predictable growth rates you will become better at planning your pruning.

Since you have proven that your tanks have enough light to produce bushels of vegetation, I tend to find suspect suggestions that you need more light. As the days get warmer you might consider increasing your day length. Ten hours is on the short side, twelve hours might be better.

Judging from these photos and your AGA biotope entry I would generalize that you have tendancies towards letting plants lay over. Most fish like the darkness this provides and show off iridencense well in such conditions. However, pruning such a tank tends to be infrequent and severe. It tends to result in large changes of plant mass that can produce temporary chemical imbalances.

In the intrest of producing both a steady environment for my fish and an always stunning display, I choose to prune a little bit several times each week. Typically I will spend about one hour every 3 days on pruning. Because I have learned how fast my plants grow I am able to rotate the species trimmed to maintain a very consistant plant mass. With this rotation I am also able to reduce the just hacked look of less frequent prunings.

In my opinion, great aquascapes don't happen until one gets their stem plants under control. The Dutch style of aquascaping is very useful template for learning how to trim different species of plants. Since they are all lined up and attempt a height taper from front to back, they provide gardeners with the combined challenge of growing both short and tall. Most species demand slighty different trimming methods to achieve this look. Additionaly, since the plants grow alongside one anouther comparative rates are easy to observe.
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Thanks everyone for the input. It just had gotten a little hectic and I had to take a break. I think I am mentally and physically recovered enough to start again. This is what I am doing now for each tank.

75 gallon. I am assuming that this is a low light tank. I have temporarily stopped dosing and co2. With the soil substrate and low light I figured it would not get much worse and I could concentrate on the 125 gallon hi light tank. Tom had mentioned a rather heavy dosing regimen for the 75 gallon tank. Tom, do you realize this tank is rather lo light? Should I restart the co2? I have noticed that the more nutrients I put into this tank the less algae I tend to get, even though it is lo light. In fact the lo light 30 gallon and 7.5 gallon (soil) tanks are doing very well with 50% weekly water changes and 10 ppm no3, 1 ppm po4, and .5 ppm Fe twice per week. So I not sure whether I need to dose the 75 or not if its lo light. I am getting a little more algae in the 75 since I stopped nutrients and co2.

125 gallon. I think I was caught in a death trap with this one. My problem was that I did not have enough healthy plant mass. I had upped the lighting to make it a hi light tank and was pumping in max co2. The plant tips were quite healthy; over the months the ludwigia repens, B. carolina, zosterella dubia, etc were growing and very gradually increasing the size and width of their leaves. The problem was that, with all the previous problems, 90% of the plants were covered in a very thick brown algae. It would be impossible to trim the plants of algae like Tom mentioned was important, without drastically reducing the plant mass again another order of magnitude. I would have had very few plant tips left. I took all the plants out of the 125 gal tank and did a thorough vacuuming, as I also have a blue green algae problem with this tank. I took all the plants outside to try to clean them, bleach, or whatever necessary to save them. But in the 95deg heat and sun, I looked at the mess and realized that it just was not going to work, and ended up dumping the plants in the compost heap.

I'm thinking the scum was biofilm, and related to the blue green algae attack. Just too much bacteria in the tank.

I then kept the light out in this tank for about four days while I rested and tried to regroup and see what I could do. The only plants that I could get for free were Bacopa monnieri in Corpus Christi, and possibly E. berteroi in the next town. The Bacopa was gone from the heat and lack of water, but yesterday I found the berteroi. It had already gone to seed but the plants seemed to be putting out new leaves, so I put on my boots and dug up about 200 plants. Although the leaes have a lot of wear and tear the plants looked like they would still grow in a better environment.

I took them home and cleaned them and covered the bottom of the 125 with the berteroi. Its funny but it looks like my most realistic biotope: with 10 inches of water in the tank it looked exactly like the ditch I took the plants from (except for the mud). I know that I will have to pull plants out as they spread out and grow but it just might be enough plant biomass for now. I took out the fish so I could max the co2 without killing any fish, and I was going to start 10 ppm no3, 1 ppm po4, .5 Fe from flourish twice per week with 90% weekly water changes.

Any advice? Tom, the two 175W MH are about 5 inches from the water and the 96W AHS is about 4 inches away. Tell me (exactly) what to dose. The co2 will be high.

I do realize now that aquascaping (gardening) is important to the health of a tank and will try my best.

And once again, thanks everyone for the advice. You people and this forum are the best place on the planet for this kind of advice.

Steve Pituch
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Steve Pituch said:
I'm thinking the scum was biofilm, and related to the blue green algae attack. Just too much bacteria in the tank.
I've noticed similar correlations.

I think 10 inches of water in that tank has great potential. If I was starting a new tank today I would set it up only 1/3 full by design.
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