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low light

4475 Views 17 Replies 10 Participants Last post by  Steve Pituch
What types of plants would do best with low light (15watt in a 20Hgallon)?
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um....Moss, java fern and anubias. And that is pushing it. You are really at the "almost not enough light to sustain" level. Not sure if 15 over a 20 will even grow really...perhaps on the several month time scale.
I'd have to recommend the plastic varieties, regretfully.

How good are you with wiring? Theres many DIY ways of getting more light. The AHSupply 55w DIY kit would upgrade your lighting fairly well. Or you could DIY using standard normal flourescent tubes, of even overdrive them.

Also, if it's a stock hood, theres usually upgraded light boxes that contain dual-bulbs instead of single, etc...
Well about the ones on that link for sale, Im kinda on a limited budget for aquarium keeping right now(who isn't?) And as for wiring and other handyman stuff im not so good at for DIY projects.

I havent found any upgrading boxes or anything to change the current hood- its a perfecto(brand) hood btw so if you see anything that could upgrade it please let me know. Thanks
Probably some of the Cryptocoryne, such as C. beckettii, C. walkeri (lutea) or C. wendtii, can hold their own under those conditions. The old fashoned large amazon swords, Echinodorus amazonicus or E. bleheri are also quite tolerant of low light. If you can get it, try Hygrophila polysperma. If that can't grow, then you are really limited to the lowest of the low light plants, such as Microsorum (Java fern) and the above Crypts. . If H. polysperma can grow, then probably Bacopa carolinia can, too.
Pearl grass, Hemianthus will do.

I grew some at less than a w/gal at 24" depth.
But had CO2 and good nutrient levels also.

If you want to have low light, that's fine, but you'll need to make sure you good CO2/nutrients also to maximize the low light efficiency for the plants.

Tom Barr
Hi fish4brains:
I have the same tank with a 15w GE Aqua Rays F15T8-AR-FS light bulb.
My substrate is 1 1/2" regular aquarium gravel over 1" garden potting soil, the tank has been set up this way for over a year. No CO2. The plants I have in there now are:

Hygrophila polysperma
Hygrophila difformis
Ludwigia repens
Microsorium pteropus "windelov"
Rotala rotundifolia
plant sold as Shoestring Sagittaria (not sure what it is?)
Cryptocoryne affinis
Cryptocoryne sp. (dont know)

I've grown before in here:
Anubias nana
Cabomba caroliniana
Ceratopteris thalictroides (which stayed rooted, and had the thinnest multipinnate dark green leaves I've seen.)

Yes you can grow plants in there. Everything grows slow (except the H. polysperma), but its easy to manage.
This is just my experience....
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In my opinion there are such a group of a species which can grow in these conditions without health problems. They can give you enough biodiversity and you will no have the real and constant problem of common pruning, but I would like to emphasize and comment here some landscaping difficulties:
1- most plants grow upwardly giving the same repetitive image on the tank and hiding peculiarities of species morphologies
2- is difficult to make a bizarre carpet, so the substrate is frequently visible in excess.
3- is difficult make contrasting landscape units at different levels, because the plants don't agree with an extra shading.
Yours. Maurici
plant brain- do you have any other info as to how to raise the pearlgrass such as lighting ,fertilizer,etc? and can it be used as a foreground plant?

Neonfish3- what do you use for the foregrund plant in your tank and does it grow rapidly like the other high-light kinds?
Yes, it is a foreground plant.
It grows slower, but it's still nice looking.

Follow general non CO2 methods.
Good substrate, I use onyx(3-4") and peat(1") and don't do any water changes.
I might add a little SeaChem Equilbrium once every 2-4 weeks, I feed fish regularly, since that is the main fertilizer for the tank.

Tom Barr

I have a question on your low light tank. You mention 1 inch of peat. I need to set up a 30 gallon tank as low light, and since I have had problems before with over active soils, I was wondering which peat you use and what is the procedure. Is it Sphagnum moss or regular peat moss from the nursery? Do you soak it, and for how long? How do you keep it from floating up into the tank? Do you pack it wet to 1 inch depth, or lay it in dry? I need a substrate less active than the previous ones that I have tried.

I just bought a 95W AHS kit for it. I based the choice on length of the tank. I think I will need to use the glass top and hang the light 1.5 feet from the lid in order to reduce the light. I want to keep crypts in a low maintenance environment without CO2 supplementation.

Steve Pituch
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plantbrain said:
Yes, it is a foreground plant.
It grows slower, but it's still nice looking.
How slow does it grow? How slow do you think itd grow under 15w in a 20gallon?
plantbrain said:
Follow general non CO2 methods.
Im using CO2, is the care any different if i dont have the fert.-rich substrate, but im using a weekly fert. called plant grow. Thanks for the help.
plantbrain said:
If you want to have low light, that's fine, but you'll need to make sure you good CO2/nutrients also to maximize the low light efficiency for the plants.
Tom, can you elaborate on this point about CO2, low-light tanks? How does one maximize the efficiency?

I'm growing mostly crypts, java ferms, moss, got 2 stalks of Barcopa Caroliana and some H. Polysperma too in a 15gal with 20W FL with moderate fish loading...

I know it was stated that Fish4Brains isn't much of a DIY project guy, but if you could, you might want to look into ODNO. Could possibly overdrive your existing setup for dirt cheap and get much more wattage.

Ahh, too many voices:)

Okay, the pearl grass grows at a good clip, not like CO2, but it grows faster than you think.

Maybe like hairgrass in a CO2 tank, about that same speed.

You might try plain old ground peat from the nursery, I hate sphag personally. You could also try some leonardite too.
Barley straw pellets, soil will work well if you soak it 2-3 weeks and then add about 1/2-1".
I soak the peat first. Maybe a day or two.

You can vary the amount of peat etc which I think works better than soil in a non CO2 tank to suit your taste.

I really like onyx over the longer term with non CO2 tanks.
Flourite was/is good also.

I add about 4x the normal amount of peat in a non CO2 vs a CO2 enrcihed tank.

You can dd a number of different organic matter sources.
Leonardite will take longer than peat that will take longer than soil, that will take longer than mulm and detrial materials to decompose.

Peat is right in there. Neil's had a peat tank running for a decade with good consistent growth. No gas.

You "maximize" and maintain the light use efficiency of your tank.
I think that should be the goal for any plant tank.
That goal is easiest to attain at low to moderate lighting.

But if you want to get everything out of a small amount of light, adding CO2 will help take the pressure off this low light "stress" allowing wonderful growth at lower light levels.

This also means less algae growth and plant growth but still have nice appearing plant growth, just slower.

A shop light over a 55 gal and some flourite and good CO2/nutrients once a week with 50% water and a good sized fish load works very well.

But you could add more light and get more out of it. I'm just giving you some options if you want to improve plant growth besides the obvious addition of more light.

Tom Barr
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Thanks for the info on the peat. My next question is light. I bought my first AHSupply 96W light kit, for a 30 gallon tank. I bought the 96W setup because of the length of coverage for a 36 inch long tank. I figured that I could always raise the light if it was too much light. Well these lights have got to be efficient. I am burning my retinas looking at this tank. Below is a picture of this tank and to the left is my AGA 7.5 gallon bowfront tank with an old darkened GE 9325 Aquarays 15 W bulb. The bowfront has been my best low light tank now for several years. So right now the 30 gallon tank is a very high light tank. (Yes, the light is on in the 7.5 gallon tank!)

So I plan on raising the light fixture. However I am getting a lot of shadows from the glass cover. I usually don't use glass covers but since it is going to be a low light non CO2 enriched tank per Walstad, I am supposed to use a glass cover to keep the co2 in the tank. It would be best if I got rid of the glass covers though. You are saying that aeration will increase the co2 in a non co2 enriched tank. I thought that the plants would get co2 from the breakdown of the soil and this gas needs to be conserved by the use of a glass cover. But you say its best to aerate the water to get more CO2, and that seems to be contrary to what Walstad has written.

Once again I would like to get rid of the glass covers, especially if it was on a low light tank. I think this would really look cool.

Yes, the light is on in the 7.5 gallon tank!

Top view of the $5 enclosure

Top: 96W bulb, bottom: 30 W T8

Steve Pituch
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Can't you use that 96 watt retina burner on a tank you want to be a high light tank? It seems like such a waste to cut back on all that light so that you have a low light tank. You are going to have to raise the light four or five feet above the tank!

I have seen three foot 30 watt T 12 fluorescents. They are not common, but you could probably find them at Home Depot or some kind of electrical outlet. One or two of them would be just right for your 30 gallon.

The organic matter in the soil is not going to produce very much CO2 for very long. After a few weeks, most of the CO2 will come from the fish food, and that will not be very much. The plants during the day can lower the CO2 content until the partial pressure of CO2 in the water is actually less than the partial pressure of CO2 in the atmosphere (about 0.2 mm Hg). Under these conditions, aerating the tank will increase the CO2 levels. Only plants that are adapted to growing in crowded, sunny ponds, where there is little or no water moving through and competition for CO2 is high are able to extract enough CO2 to grow when the water is in equilibrium with the air.

Of course, there is no reason why you can't have a high light, non-CO2 enriched tank. Good plants for that would be Eigeria, Najas, Vallisneria, Ceratophyllum. There is a danger of the pH getting too high for fish in a tank like that, however. I once had a tank like that, with some zebra danios, and, one day I noticed one fish dead, and the others looking sick, and the pH turned out to be 9.6. The other fish recovered when I got the pH down to between 7 and 8 with CO2.
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Hi Paul,

Part of the reason is that that the 30 gallon is in the back entrance away from the other tanks, and is not near the co2 tanks. Its the one that my son had salt water in when you were here. I had two 30W T12s on it and was fertilizing the same as in my co2 hi light tanks. The substrate was Schultz. A few weeks ago I added another 30W T8. The becketti, cabomba and hygro grew beautifully for two months. I was very pleased with the results. Then one day I looked at the plants and the becketti has completely melted and the cabomba had no leaves, just rotting stems. Much of the hygro was dropping dead leaves. The only thing I had done differently was to not add Chloramine remover at the last 90% water change since I had no fish in the tank.

I have had entire tanks of plants die after water changes before. (I was using chlorine remover, not chloramine remover). I have even had anubias leaves totally dissolve in a few days. It is like putting all the plants in the 10 minute 1:20 bleach/water solution. Everything dies.

The last time it happened I added more light and nutrients. Since I had been adding the nutrients to the 30 gal tank I figured it was the light. However, from experience I know I do get several ppm ammonia when I use a chlorine remover instead of a chloramine remover. Could the ammonia be killing the plants?

Also the 96W of light is unbelievably bright over the 30 gal tank. Is this what people mean by hi light? To me its like 6 W/g compared to my hi light tanks. What I would do if I keep the 96 W light directly on the cover glass is to move the tank so I can supply co2 to it. But I figure at this intensity I am begging for algae problems.

I figured the 55W or 36 W bulbs would not have given me good end to end coverage.

Steve Pituch

PS: I just put the two 30W T8s back in over the tank, and added a lot of Bolitus, Java fern, and C. Wendtii. I figure the only thing that is missing is carbon, since there are no fish in the tank. I will get some guppies or platies for the tank and start feeding fish food. Since I only have two 175W MH pendants over the 125 gal tank I put the 96W fixture over this tank at the center. The lighting is much more even now over this tank.
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