I have an AC50 on my 20 gallon long. If I were to run one filter, I would get an AC70... I'm thinking about running two AC50's. You can see it in my signature if you like...
My params are always 0 A, 0 NI, low NA because it is planted, but I like really clear water! The single AC50 I have running with a sponge and double bio is not doing that. Here is my suggestion...
Run two AC whatevers (I would even venture to say two AC50s is just grazing the surface of over-filtration, you could even go bigger), fill one up with a double sponge insert and a fine filter floss, and the other one sponge insert and the rest bio material (or one part chemical filtration, if you prefer). That way, you get plenty of mechanical filtration and bio filtration... the sponges will totally act as bio filters too. Also, you can run one intake all the way to the bottom of the tank, and one in the middle, filtering different water columns. Alternatively, run both double sponge with a single layer of bio material.
AC filter are MUCH more efficient mechanical filters when they have two sponges, and running two filters is always a good idea in case one crashes for whatever reason.
You clown loaches will not mind the flow (I have kept 3 species of botia, including currently keeping clowns)... they actually really like it, and will swim in it. They swim straight into the output of my FX5 on my 125 gallon with joy! Ha.
Just please have at least 100 gallons for them waiting.
