hey amigo, may i reccomend a much larger tub? im not sure what kind of light youre using, but other than the cost of nutrients there is really no downside to using a larger one, and you will not have problems with the temperature of your reservoir creeping up over time. Once it gets over 72 farenheit the water doesnt hold oxygen very well, and bacteria of the anaerobic variety start to thrive. Believe me, this is no joke my entire 18 site grow op is in jeapardy due to this. Also, definitely run the pumps 24/7, its not an option to run them less. Good luck. By the way, if your having problems growing in soil you should try 1 part sphagnum peat moss, 1 part vermiculite, 1 part perlite with some miracle gro moisutre control soil (mostly just sphagnum peat with little bubbles added in) also. Its really much easier than hydro, just takes us more space. although i like my hydro setup, its one headache after another till you get some experience under your belt. Just food for thought. Good luck.