Hi Karen,
I've got one semi auto CO2 set-up and the other set-up is DIY (the old 2 liter bottle, sugar, yeast & water thing). The DIY thing is not good for a moderately to heavily stocked tank as water acidity tends to fluctuate because it continues to inject CO2 even at night, when the plants themselves are respirating CO2. For ferts, I use PMDD (poor man's dosing drops) which you can make yourself. I get my ingredients from a guy over in Iowa. I also try hard to keep phosphates and nitrates as balanced as I can. (water changes frequenty since it's difficult to control nitrates any other way IMHO) Either one gets out of whack and voila instant algae bloom. Lastly, a whole lot of light. On top of the 180, I've got two 36" twin tube flourescents, two 36" Power compacts, and two 36" single tube flourescents. On the 75, I've got a four-bulb power compact. Both tanks are on timers for 11 hours a day.
Mellonhead,
I will put together something on how to put together tile caves... if that makes any sense at all
regards
mike