Don't know much about sponge filters... Couple questions...

Starting to put together pieces on my 40 breeder, as some of you may have seen in my other posts... Got lighting, and substrate pretty much squared away... Filtration I've got a couple questions about...

I'm going to start it as a shrimp-only tank until My plants get good and established the way I want them... I found a decent deal on 4 of the double sponge filters on Fleabay, and I know how they work, but that's about it... When I add fish later, I may switch to HoB filters (probably dual AquaClear 50s), or if the sponge seems to work fine, just leave them in.

Thoughts/questions:
1. Tank has left side and back to the wall, thinking about putting two sponge filters on the left glass, two on the back glass. Would this be good, or would I be better off with all 4 across the back wall? Does it matter?

2. Would they be better running off a single output air pump and 4-gang valve, or a dual output pump with two 2-gang valves? Does it matter?

3. What kind of output/cfm should I be looking for? Should I just go with the gallon (good up to 40g, for 12-93 gallons, etc.) ratings on the air pumps? The double sponge filters are rated for 20 gallons each, so I should be over-filtered...

These are the filters in question:
http://www.ebay.com/itm/4-pcs-Bio-S...-Fish-Tank-Double-Sponge-XY2822-/261031309992

Thanks!

Curtis Rouse said:

Instead of doing sponge filters then switching to a hob or 2 down the road and risking another cycle and costing you more money why not get the hob now and put one of these prefilters on the intake tube?
http://www.amazon.com/gp/aw/d/B002LL32RY

Sent from my mind to my fingers to my phone to the MFK servers to you

Click to expand...

Just trying something different, and space constraints. The back of the tank is pretty close to the wall, I think I've maybe barely got enough room for a HoB, will have to double check the space... Lots of people seem to use the sponge filters for shrimp tanks, and it'll probably be a shrimp-only tank for a few months, since I want to get plants established, and shrimp breeding before adding fish. Like I said, if they do well, might just stay with the sponge.