Dryfast foam filter

[heronfeeder]

This is a question about using Dryfast cushion foam as a filter medium. About 20 years ago, I built a pond in New Orleans and made a filter system using perforated PVC tubing and blocks of foam rubber. It sort of worked but the foam rubber was so fine-grained and soft that it very quickly became clogged and collapsed on itself due to the suction. I was familiar with Dryfast foam through boat cushion use and tried blocks of it as my filter medium. It worked spectacularly well except that within a few days all my fish and pond plants died. I had neglected to take notice of the fact that the foam was anti-microbial treated. I didn’t want to give up on the foam so I soaked the filter blocks in water with detergent for a couple of months hoping to remove the anti-microbial treatment. After a test with one “volunteer” goldfish, I found that the treatment had removed the anti-microbial compound and the foam was now safe for use. Twenty years later that foam has reached the end of its usable life and I need to replace it. I bought some more Dryfast foam and I’ve started soaking it in detergent water (Tide plus OxyClean), but I’m curious whether others may have experience with this and know the best way to treat this foam to make it safe for use. Another goldfish will be volunteering in a couple of weeks to be the canary in the coal mine.
Apologies if has already been discussed. I tried several keyword searches and found nothing.

 

[Mmathis]

Hello and welcome!

I have never heard of it. Seems like it would be a good “fines“ filter media. Have you tried contacting the company for advice?

 

[heronfeeder]

Yes, it is a very effective filter. Both mechanical and the 8 blocks of foam that I use have over 2800 cubic inches of coarse media for a biological filter. I just rinse them out about twice a year. I did ask the manufacturer about treating this for use as a pond filter. They chose not to respond, which is pretty reasonable since this isn't their target market and they wouldn't want to be responsible for killing someone's prize koi.

 

[j.w]

@heronfeeder
Don't know about that stuff. Looked it up and this is what I found. Looks like it would be a good filter for fines. Is it easy to clean off when it gets full of gunk?

 

[heronfeeder]

I consider it pretty easy to clean but not everyone might agree. I blast the blocks with the hose and then squeeze them under progressivly cleaner water a number of times. Sometimes I throw him in the clothes washer with cold water and no detergent. That gets them clean.

 

[Mmathis]

Do you wash them with regular tap water or water from your pond? I guess it doesn’t matter if you have an alternate biological filter, but if this is your bio filter, you are doing major damage to the pond’s ecosystem — every time you wash, your pond would basically have to go through another cycling. You know, I have wondered about the washing machine, but I figured that even if you don’t use soap, there might still be some residualdetergent in the washer. IDK. Maybe someone else has an opinion about that.

 

[heronfeeder]

The first time I cleaned them I used pond water. Then the second or third time I used tap water, and didn't notice any difference in the health of the pond. Since then I've always used tap water. No longer in New Orleans, my pond here is very shaded without any water plants. I have a 500gph pump in a 1000 gallon pond. The water is clear most seasons and the goldfish make babies every few years.

 

[heronfeeder]

In case anyone's interested in what these filters look like, here's an image. These foam blocks are my old ones (in use 19 years) and measure about 4"x5"x10". The replacement blocks will be about twice that size but use the same plumbing.

 

[heronfeeder]

The switch to newer and larger foam filter blocks went well and the pond has been healthy for over a year, including through an uncharacteristically hard freeze last winter. A couple of months ago I adopted some fish from a neighbor who moved and lost his pond--four fish including three goldfish and one koi--all a bit larger than the thirty goldfish I had. Though these new fish didn't eat much, I thought all was OK until noticing this morning that they had eaten my filters. The ragged remnant in the image was until recently a rectangular block. These fish are now heading toward a new home, but I can't understand what motivated them to eat foam rubber, full of algae no doubt, but still not so nutritious.

 

[Lisak1]

Very interesting set up. I"m glad you shared a photo as I had an entirely different picture in my mind!

As far as what would motivate fish... who knows! I'm guessing it was the algae, and once they got started it just went south from there!