I have a 4200 gallon pond (approx). I have a 2000 ultima II filter, 5000 submersible pump, 4000 submersible pump, and a 80 watt uv light. I backwash my filter almost everyday and the water draining out of the filter is always black. The 5000 pump is the only one hooked up to the filter along with the uv light. Is the problem the quantity of fish (goldfish and koi) or is the pumps too small? I also have a air pump in the pond. I also installed a milk crate and placed the 5000 pump in it and the entire crate is covered with quilt batting. The water is somewhat clear (I am able to see the fish) but I am not able to see the bottom of the pond. This may be due to river rock on the bottom? Thanks for any help.

What is the quantity of goldfish and koi in the pond (number and size)? Unless the pond is severely overcrowded, your pumps and filter should be strong enough. Is the 5000 pump 5000 gph? If so, it should be enough. I'm not familiar with that filter. What kind is it, bubble bead? They tend to trap more and need more frequent backflushing. You might consider a separate more traditional filter with bioballs, brushes, and/or other filter material. I have my pump in a plant basket (with holes) and wrapped with filter material so you have something similar. That should lessen how often you have to clean that part of the system. River rock on the bottom sometimes makes things clearer (as it has places for good bacteria and other life to grow) but can make things worse if there's a lot of old debris and waste trapped among the rocks. What kind of plant cover do you have? Is the lack of clarity in the water due to suspended algae or something else? If it's algae, see http://www.fishpondinfo.com/plants/algae2.htm for natural ways to combat that.

Robyn, when a UV light kills suspended algae, what happens to the dead algae. Would it get trapped in a filter, is dead suspended algae possibly black?

When I clean my filters, the debris is always brownish, not black.

Thanks,
John

Dead suspended algae could end up anywhere in the pond - in the filter, on the bottom, floating around even. It can be green, brown, or black depending on how long it's been dead and how dead/damaged it is.

Pardon my ignorance, Is suspended algae another term for hair/string algae?
Thanks.
Karen

No, hair/string algae and suspended algae are two different algae. Hair/string algae are attached and grows long like hair. Suspended algae are just that, suspended particles in the water.

Thanks Johnnyboy.

I have a ton of string algae! I have been pulling it out by hand. I added barley/peat liquid just the other day.

I started my garden off with loads of string algae, when that pooped out I watered my garden with the suspended algae that was from my seriously green pond. When I first planted my tomatoes my hubby laughed at me. Next year he's going to tie them up for me ( I'm thrilled <_< ) lazymans way is alot more fun.

So Sadie Mae, are you saying to use the algae for fertilizer?

Yep, the dried up algae makes great fertilizer. I don't do any special, just whip the stuff on the ground surface/grass compost I have down. It's already vitamin packed because of the fish poop. :D This season I didn't do anything special ( to hubby's surprise). When I plant my tomatoes I always put some slow organic processed fertilizer then supplement with the algae goo during that part of the season. And I think I may have watered about 3 times with pond water, only because I was working on the waterfall. I don't do any extra watering and plants are huge and only found 1 slug ( thanks to all the birds ). I don't do ANY chemicals especially being 1 foot from the pond edge.

Thanks Sadie, Normally I just pull it out and toss it somewhere, but now I will put it in a bucket and dump it on my compost!

However, I do have a TON!!of slugs!

I've seen a few bite marks in my tomatoes ( which I just slice around ), but only one actual garden slug. But it you have TONS...it's time for a party and to share the beer. I hate the method, since I know they actually drown, but it's pretty surefire method to get rid of them. They love beer.

Oh Sadie, I won't kill anything. We will have to live peacefully together. Aren't they good for the ground? like worms?