Issue with prefilters on AC20 filter

Chickadee · 2026-09-23T10:03:53-0500

I have AquaClear 20 filters in both tanks. To keep future fish/shrimp from getting sucked in, I bought some prefilters specifically for AC filters. They fit okay except for one problem. There is a hole at the tip of the siphon tube and also a hole in the prefilter. This leaves a tiny opening on the bottom that I can almost fit my pinky finger into. I'm concerned something could still get through there. Could I close this hole with super glue maybe? Are there other prefilters that only have a hole at one end?

Tomsfish · 2026-09-23T10:47:30-0500

Look up stainless steel or sponge prefilters for aquariums and there will be many choices.
Pawfly was one name of a single hole sponge on Amazon.
I used both of those on my aquaclears.
For the 20 I think the smaller ss screens are the size [ 11mm ] the pawflys were small enough.
The sponges come in multi packs that are cheap.
You could cut some sponge, filter fabric or floss to stuff in the hole temporary but long term you will be better off with the single hole sponge you want.

TwoTankAmin · 2026-09-23T11:25:17-0500

I had 28 running ACs at my peak. All of them had a pre-filter. Only my one 110 used and ATI pre-filter. I also use the ATI pre-filters on my canisters and powerheads. They come in different sizes and also come with a series of adapter to attach them to intakes.

I make my own pre-filters. When I started I used a block of AC foam for a 110 even though I did not have one yet. Some years ago I discovered Poret foam and began using either the 10 or 20 ppi foam. The lower the ppi the coarser the foam. For your application I would be more inclined to use the 20 ppi. I might even consider a 30 ppi.

The problem with pre-filters is they need to be rinsed every week. If they clog they slow or even stop the flow into a filter. If I had a video camera (I do not use a smart phone) I would make a vid showing how to make a pre-filter which will cover the open hole at the end of the AC intake tube.

Beciasally I start with a rectangular block and then use a sharp scissors to cut an X into the block. I cut most of the way down towards the bottom of the block but stop cutting 1/4 -1/2 inch before I reach the the bottom of the block. The X cut is why you can slide the pre-filter onto the tube and have it stay in place.

Next, I use the scissors to prune the block so it is more circular and has a rounded bottom as well. You can see the end product in the picture below. That is actuially an AC 20 whicc when I bought it was called a 100 which is its GPH rate

You can see all the ATI pre-filters and parts here https://www.aquariumtechnologyinc.com/filter-max.html#/
I would suggest you get either the Mini or the #2 pre-filter. I have never used a Mini preferring the #2.

Here is a pic of muy 150 which has the 110 on it as well as an Eheim canister and a H.O.T. Magnum all of these are pre-filtered. The 100 prefilter is ion the right end of the tank belowbetwewen the plants. The adapters that come with the pre-filters allow one to use the foam placed vertically as below or horizontally. I eventually got a bigger foam for this tank and changed it to a horizontal orientation.