Hi everyone! I set up the tank yesterday
I will post a picture later today, but for now I will tell you guys a little about it. The tank had 6 cups top soil and 4 cups pool filter sand put into it...the resulting layer was supposed to be just over an inch thick, but it's significantly less than that now, likely (A) because the sand partially mixed with the soil, and (B) and soil compacted a bit when it became wet. I planted most of the plants before adding water to the tank...the plants include Cryptocoryne wendtii, Hygrophila difformis, Ceratophyllum demersum, Golden creeping jenny, and an unlabeled pink plant that is likely Alternanthera reineckii. I had no issues with anything floating, not even the orchid bark (the topsoil I used seems to be quite heavy...even when it was exposed while filling the tank, virtually none of it floated).
As or water parameters...PH is only 6 and KH is no higher than 1, even though I added a half teaspoon of baking soda and 5/4ths tsp marine salt to this five gallon. I believe something in my tap water reacts with baking soda; even when I add 3/4ths tsp baking soda to 5 gallons of water here, the KH only rises to 5 degrees. I tried my planned CO2 method yesterday and it did not seem to affect the tank...I put several inches of sand over the baking soda and citric acid and when I emptied the container today there was a foam at the bottom of the container today, so I believe the CO2 generated was unable to rise through that much sand. I will try a few other configurations today, and if this keeps happening I will be back to the drawing board with generating CO2.
I did think of a possible second option for generating CO2 in this tank; calcium carbonate also reacts with citric acid to form CO2, so if my first idea continues to be ineffective I am thinking of adding a small bag of oyster shell or similar to the filter and directly channeling citric acid through the filter.
EDIT: Just discovered a problem...my ratio of reactants was wrong! The ideal ratio is about 1 part by volume each baking soda to citric acid; 1/4th tsp each is sufficient to produce 1.435 grams of CO2, or almost 76 mg/l for my 5 gallon.
EDIT no. 2: I reduced the thickness of sand in the reactor, and it's producing CO2 now! The co2 test I got (which I calibrated to react at about 10 ppm CO2) has turned from deep blue to a more greenish blue color, suggesting that the CO2 level is higher than the equilibrium CO2 level of aquariums but not quite at 10 ppm yet (my second CO2 test, calibrated to the normal 30 ppm, has not changed). Some of the CO2 is bubbling out of the reactor, so I think I am going to add some polyfil to the top of the container to slow down its escape and give it more time to dissolve.