Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Can you describe better the light?
If it is fluorescent, what size is it? T-8? T-5? Other?
I would add a slow release fertilizer tablet near the plants that are currently growing, as deep under the sand as you can.
Then research a few ideas:
Substrate: Sand does not hold nutrients the way better substrates do. Cationic Exchange Capacity (CEC) is the key here. Substrates with finer particles can hold onto many of the minerals that plants use to grow, so that it acts as a reservoir, and makes growing the plants easier.
Lighting: PAR is the photosynthetic activity of the light. What color light energy plants use to photosynthesize. Plants mostly use certain wavelengths of red and blue, not so much yellow or green. Our eyes see yellows and greens better. Light designed for our eyes will be high in the yellows and greens, not so rich in the reds or blues.
I set up tanks with one of each: A plant specific bulb that has plenty of the reds and blues, but looks sort of dim and purplish to me, and a 'daylight' sort of bulb that has a more complete range of wavelengths. Makes things look natural in the tank.
CO2: The easiest source could be one of 2 methods:
There are liquid carbon sources that most plants can use. Seachem Excel is one.
You could go pressurized with a paintball system. It is small, easy to fit into a dorm, and a reasonable supply for a small tank.
Fertilizers: The simplest way is to continue with the substrate tablets. They can be a bit expensive, but for a 5 gallon tank it is not much.
The cheaper way might take a little set up. I would buy a small bottle of each nitrogen (N), phosphorus (P) and potassium (K) and a trace mineral supplement such as Seachem Comprehensive (trace). Use the liquids, and get a feel for how much your tank needs. (Seachem is not the only company that makes fertilizers, I have used them and am more familiar with them)
Then buy the dry powders and refill the bottles as needed. When you refill you can mix the N, P and K sources in the ratio you have found your tank needs, and have one bottle for these macro nutrients, and one bottle for trace nutrients. Do not mix macros and traces. This will ultimately be cheaper than substrate tablets, but the initial cost will be a bit more.