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Discussion Starter · #1 · (Edited)
I'm considering adding an HOB overflow/skimmer box onto my 30 gallon FW tank (flat back hex), and am curious if I can use my canister filter with the box, or if I should switch to a sump. I wouldn't mind switching to a sump actually, but in the meantime it would be nice to use what I have with my current setup.

Also, since overflow boxes skim the surface, as opposed to drawing intake water from the bottom of the tank, doesn't this adversely affect filtration of the mid and lower tank levels? Has anyone here ever tried to using both a canister with regular intake AND an HOB skimmer? Plumb in a tee fitting for two inlet branches into the canister with a ball valve on the overflow box inlet to control flow. Seems like this would work well. Best of both worlds.

I noticed several vendors are discontinuing the CPR overflows. I wonder if this is due to customer dissatisfaction or if they're coming out with a new version.
 

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Depending on how the overall current/flow in the tank is, I don't think a skimmer in itself would diminish your filtration. I would say that I think hooking a canister to the overflow could be problematic because of the potential to get air into the canister. You could get enough air in to lose the prime and potentially do some damage to your canister. I suppose it's possible if you can get an overflow that would flow in excess of the canister's max flow rate. Evaporation could also play a large role in how well the system works. A sump addresses both of these concerns.
 

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Discussion Starter · #3 ·
Depending on how the overall current/flow in the tank is, I don't think a skimmer in itself would diminish your filtration. I would say that I think hooking a canister to the overflow could be problematic because of the potential to get air into the canister. You could get enough air in to lose the prime and potentially do some damage to your canister. I suppose it's possible if you can get an overflow that would flow in excess of the canister's max flow rate. Evaporation could also play a large role in how well the system works. A sump addresses both of these concerns.
Good point about the air getting sucked into the canister. Didn't think of that. Maybe I'll use a smaller canister in tandem with a sump. Canister to draw return water from the lower levels of the tank and do the bulk of my filtration, and an overflow with sump to surface skim and keep the top layer of water crystal clear.

Depending on how the overall current/flow in the tank is, I don't think a skimmer in itself would diminish your filtration. I would say that I think hooking a canister to the overflow could be problematic because of the potential to get air into the canister. You could get enough air in to lose the prime and potentially do some damage to your canister. I suppose it's possible if you can get an overflow that would flow in excess of the canister's max flow rate. Evaporation could also play a large role in how well the system works. A sump addresses both of these concerns.
I meant in general, for those of you that use ONLY an overflow, don't you have excess buildup of waste on your substrate since there is no intake in the lower area of the tank?
 

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I have a 75 planted with a 40 gallon sump. I only use a single return and with plenty of flow, i do not get any more detritus on the bottom than i did with 2 canisters.

Why use a canister and sump? My overflow dumps into my sump, water has to go thru a 2inch thick wall of 10 ppi poret, then thru a 2 inch wall of 30ppi poret. Easy to clean and maintain and my tank water is crystal clear.

The sump was one of THE BEST things i have done to my tank.
 

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get yourself a surface skimmer. it will draw water from the surface as well as about 12" down. glass ones are nice, but fragile. i tend to have more water taken from below than the surface. it prevents air from being drawn into the canister. the skimmer will help with co2 outgassing, but that's necessary to help balance and stabilize co2 levels.
 
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