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Old 11-19-2012, 07:31 PM   #10
Hoppy
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Is that a 36"L x 15"D x 20"H tank? From http://www.plantedtank.net/forums/sh...d.php?t=189944 each 36 inch long Finnex RayII light is giving you about 50 micromols of PAR, so two of them together is giving you nearly double that much PAR, which is very high light. The T8 light is just along for the ride. With that much light, even with half that much light, you need to be supplying non-limiting amounts of NPK and trace elements, so the plants growth rate isn't limited by any of the basic nutrients. And, very important, you need to also be providing an optimum amount of CO2, also to keep CO2 from being what limits the plants growth rate. You need the light to be the only limit on how fast the plants can grow.

You can't use bubble rate to determine if you have enough CO2. For that you need to start by setting up the tank so the fish can live with relatively high CO2 concentration. That means the tank water needs to be very well oxygenated - lots of dissolved O2 in the water. You need to arrange the filter return flow so it keeps the entire water surface covered with ripples, no splashing, but lots of ripples. And, if you are really serious, you will also set up a wet/dry filter which does a great job of getting oxygen dissolved into the water. Now, slowly increase the CO2 bubble rate just a little bit. Then watch the plants and fish for a few days, watching for improved plant growth/health. If you see an improvement, you didn't have enough CO2 before. (Watch the fish looking for obvious distress from the CO2.) Repeat the small increase in CO2 bubble rate and watching the plants and fish until you don't see any improvement in the plants, or until the fish are showing distress. Back off to the last bubble rate and you are at the optimum CO2 concentration.

With healthy growing plants in the tank, you should be able to avoid algae, or at least make it easy to control it by cleaning it up the moment it appears. It is best to do this with no algae already in the tank. All of this works best if your tank and filter cleaning is done regularly and well.

Of course, you can also reduce the light intensity by raising the light, by using fewer lights, or by putting a layer of fiberglass window screen over the light to "filter" it. That reduces the plants need for CO2, so maintaining enough is far easier.
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