I'm new to this,just started a 29gal freshwater aquarium 2 1/2 weeks ago, been adding fish 4 at a time over 3 day period , (up to 6 neon tetras,1 Beta, 5 zebras, 2 danios, 2 catfish& 2 danio's not sure what they are, but were free ) after about a week noticed water level dropped a inch or so in...