new DIY 75g corner filter. <$20

[Digital]

I did a corner filter previously in a 40g that I have decided would need a little more horsepower if I copied it in a 75g. Well, here it is and basic specs below:

- 160gph powerhead with air line option to help aerate.
- 2" thick foam.
- 5" radius corner filter.
- 1/2" pvc pipe

The drain pipe behind the foam has about 50 holes in it so that water from the entire height is draining into the pipe. I was worried that if I left the 90 degree elbow open at the bottom it would only draw water through the filter at the bottom. hopefully, this keeps the water flowing uniformly through the entire height of the filter.

The foam was about $12 and was large enough to make 2 of these, and several left over pieces that will get tossed in a canister filter in need of media.

Comments are welcome. I need to clean the pool filter sand when it isn't below freezing outside and I'll get to fill this up and see how it works.

 

[b considine]

Just curious: Why is the return outside the filter? Why not set it up so the powerhead returns either over the top of the foam, or through the foam? Is it a space issue?

Blaise

 

[Marz]

I used glass glued to the walls to hold the foam and the powerhead behind the foam with its return poking out. I also put a plastic mesh of lava rocks behind the foam.

 

[Digital]

Just curious: Why is the return outside the filter? Why not set it up so the powerhead returns either over the top of the foam, or through the foam? Is it a space issue?
Blaise

Good question! I didnt want to have the return over the foam for a few reasons. I want to keep the foam and water level as high as possible. Going over the foam would mean I have to cut into the lid or lower the foam and water level. Also, as the water level lowers its is harder work for the motor to pull the water up and over. By going under the foam, I'm never fighting a low water level. This reasoning is why I didnt do an air driven system. You lose flow as the water level drops and the air lift cant get high enough. And finally, I can adjust the direction of the powerhead on the pipe or lower the pipe it sits on to change up how I direct water flow into the tank. I'm going to try it first with an airline connected to the powerhead for agitation of the watee surface. In a sense, its a 3 in 1 setup. Pulls water into the corner filter, provides a current for the rams, and keeps the surface moving.

 

[Digital]

I used glass glued to the walls to hold the foam and the powerhead behind the foam with its return poking out. I also put a plastic mesh of lava rocks behind the foam.

The lava rocks are a cover or to just hold more bacteria? I've thought about pouring a $5 bag of bio media behind there. I guess it couldn't hurt.

I did a corner filter a few months ago with a pipe sticking through the foam. I really didn't like how in the end I can never change the direction of the water coming out of the pipe. Once that hole is poked you're committed.

 

[b considine]

Thanks for explaining your thought processes, Marlin.

Blaise

 

[Marz]

The lava rocks are a cover or to just hold more bacteria

They are formed with bubbles, holes and cracks so they have a lot of surface area, I use them as bio filter media.

 

[Digital]

Little update -- I originally had the heater hidden behind the corner filter. it didnt work well. The water behind the filter got up to temp and would cut off the heater and the rest of the tank stayed barely above room temp (68 in basement). I was really surpised by this. Has anyone else ever tried putting a heater behind a corner filter?

 

[b considine]

I don't have corner filters, but I do use the mattenfilter configuration, with the heater on the clean side. Tanks temps are as set.

Just a hypothesis, but perhaps the return needs to be upped, so the turnover is faster.

Blaise

 

[Digital]

@Blaise

The powerhead isn't adjustable. it just runs wide open at 160gph (on paper). I think the cooler water is getting pulled into the lower inlet holes and the warmer water is just rising to the top to cut off the thermometer.

When RT warms up some in a couple months I might try putting it back there again but use a inlet pipe without holes.

 

[b considine]

Then I've got nuthin'.

Blaise

 

[zendog]

My 20 long with a mattenfilter run on a power head also does just fine with the heater behind it, but I think the difference is that it is just so much more water volume than you have behind the corner filter that the water circulate easily around the heater.

If you try it again, you might try the inlet pipe with a 45 degree elbow at the top point back toward the heater. That way it might draw water over the heater a little more. Just a thought.