All-purpose sand. I use that same substrate in all my tanks
Can't beat $2.50 for a 50 pound bag! I can't justify paying a fortune for those 'better' substrates when my plants grow beautifully already.
For a smaller tank, I think smaller grained substrates are best, because large grain substrates make the tank look as small as it really is
I'm pretty excited about the filter. Is it normal to be excited about a filter? I can't wait to start this project--It'll help me survive my final exams