best prefilter material?

**pckroeger** · 03-02-2013, 09:41 AM

I have a fine (0-1mm) sand substrate in my freshwater tank and I am worried about sand getting sucked into the filter intake.
What would be the best material to make a prefilter out of to cover the filter intake?
Or could I just raise the intake to mid tank level rather than low down near the substrate?

**talldutchie** · 03-02-2013, 10:09 AM

I find that 3 inches of the sand already helps a lot. A sponge, coarse to medium helps with prefiltering plant material. A fine sponge would be needed to keep sand out but then you'd be restricting your flow quite a bit.

**Knightia** · 03-02-2013, 11:00 AM

I have a VERY fine grade pre-filter on mine and I did find it reduced flow rate quickly. However, I have a great fix for this! Basically: put the pre-filter sponge on the intake, sliding it right on so the tube intake it snug against the bottom of the hole in the sponge. Then, when it's in position, slide the sponge down a bit (depends how long it is) to create a good "pocket" of space inside - between the end of the intake tube and the bottom of the hole inside the sponge. This will now not impede the flow rate to any significant degree.

I rinse my sponge thoroughly every week. It takes ten minutes of vigorous scrunching in a measuring jug under s running tap to clear it. Worth it though as I've not opened my cannister in two months and have crystal clear water.

**talldutchie** · 03-02-2013, 11:09 AM

Simple solutions are often the best. Wonder why that pocket of air makes such a difference though

**Knightia** · 03-02-2013, 11:22 AM

It's a pocket of water (no air). I imagine that when the intake is flush with the sponge material it blocks up at that intense suction spot and that's what impedes the flow. When it has space, the suction is spread to a much larger area through the sponge and "sucks" water in from more directions (all around the sides rather than just against one small surface) so it's more effective. I think I could explain it well with a diagram.

**korith** · 03-02-2013, 12:14 PM

A cheap diy prefilter, buy an aquaclear 20 sponge (usually comes in a pack of 2 for around $2), cut a X into the sponge with a knife (even a butter knife works) and jam the filter intake the sponge.

Also could just raise the height of the intake so it isn't so low to the ground that it'll pick up sand that gets stirred up.

Oh there are ready made prefilters that fit onto filter intakes. Usually the strainer comes off and an prefilter hooks on there. Shouldn't cost more than a few dollars, not sure.

**talldutchie** · 03-02-2013, 12:16 PM

Certainly sounds plausible.

You'd get the same result if you drilled some holes in the last few inches I think.. hmm.... got some pondering to do on this.

**korith** · 03-02-2013, 12:20 PM

I have done the same thing in the past when I used hob filters in tanks where I was raising fry or shrimp. The aquaclear sponge or any other similar sponge over the intake saved the fry/shrimp from being purified

**talldutchie** · 03-02-2013, 12:30 PM

I'm doing the same thing, coarse juwel sponge I had lying around.. Not for sand, my intake is 3.5 inches over the sand, but for plant matter. And even then, shrimp still find their way in.