best return pumps? and help with DIY sump design

Not really since it usually gasses of quite a bit of co2. Since there will probably be 250G of water or more in the system, want to retain as much co2 as possible. I am going to be using pressurized co2 if I didnt mention that, and I'll already be using a ton more than I am used too. Going from 1 75G to this 240G plus soon after I plan on running lines to a 150g and 45g so I'll be running pressurized co2 on all 3, approx 500 galons in all, I am upgrading to a 20# cylinder and will probably keep my 15# as a backup.
 
how about some pot scrubbers? they have lots more surface area than lava rock.
 
I have heard that pot scrubbers work, but I am unsure of what exactly they are talkin about - since there are so many kinds. If pot scrubbers suppose to work well then I might just do that once I figure out which ones to get.
Get the plastic/nylon ones, not the metal. I got mine at a dollar store. They came in multiple colours and had no staples in them.
 
I am better with pics ;)

Are we talking something like this:

scrubbies.jpg


Or something like this:

pp88.JPG
 
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