I have finally settled on my stocking choices for my 40B. This has been in the works since May of 2013, but for various reasons things have changed. I was going to upgrade to a 70 gallon, but considering my mom's huge fear of leaks I thought it would be safer to stick to two separate tanks. At least then if something happens to one it's not 70 gallons of water at once. For the moment I'm starting with: 10 gallon Walstad, tiny cories species only tank. Not sure which variation, yet. (in the works) 29 gallon planted, guppies (current) 35 gallon planted, black neon tetras, dwarf spotted danios (current) My 35's numbers always read great. 0,0, 5-20. It reads .25 ammonia after a large water change, but our tap water reads .25 ammonia, so I expect that. Every filter I've put in there has gotten busted, currently I'm using a bubble wand and one of these little guys: http://www.amazon.com/Aquatop-Aquarium-Driven-Internal-Corner/dp/B006QI831I Goal: 40B gallon Walstad. 12 black neon tetras, 3 dwarf spotted danios, 6 otocinclus, 10 tiny cories (variation pending.) 20L gallon Walstad. 10 tiny cories (variation pending), 10 white cloud mountain minnows I have a number of filters that I can use on the 20. Haven't decided which yet, I want to give them a nice natural river flow environment. Tentative planning to use the Aqueon QuietFlow 30. GPH is 200. My neons don't like rapid flowing water, so I keep their tank as still as possible. They are fussy, spoiled little things. I know this is sort of on the line of fully stocked vs overstocked. Wondering what everyone else thinks, they're mostly low output fish.