In the last 3 days my pond has been overtaken with what looks like brown algae. I checked the water level today and the nitrites were a little high .25. Everything else looks fine. I cleaned the filter and turned on the UV light for a day or so.

Any ideas what caused this brown algae? A week ago my water was crystal clear and had no nitrites.

Dove, can you tell us a little more. Over taken by brown algae; is it suspended in the water, or is it on rocks? I get the idea it must be suspended since you said it's clouding your water. I've never had brownish suspended algae. Cleaning filters as you did could cloud your water for a few days; all depends on your filteration system and how often you turn your pond over. Just moving the filters in my bio-fall will cloud the water, but never more than a day, and that's only if I really stirr it up, but I move a lot of water.

If the brownish stuff is on the rocks; UV won't do much good. My rocks are covered in a brownish coating. It gets thick, very attached for awhile, then sections of it will fall off, like shedding skin. I think it's good stuff, and I avoid rinsing or taking it off, but it doesn't cloud the water.

I had the same question. Is the brown in the water or on surfaces? If in the water, it could be dead algae, brown suspended algae (green algae species that appear brown), dirt, tannins (from leaves), etc. If on the rocks, it could be actual brown algae (really diatoms), dirt, or debris. Assuming that you have suspended brown algae, you would treat the situation the same as if it were suspended green algae. Namely, add more plants, have good filtration and aeration, do small water changes, add good bacteria, maybe add some barley straw, etc.

High nitrite is not good. Nitrite is very toxic to fish, moreso than ammonia. I assume you do mean nitrite and not nitrate? You can add some pond salt to reduce the toxicity of the nitrite. Do some water changes and add more good bacteria to the pond.

I first noticed it forming on the roots of my hyacynth and water lettuce and the bottoms of my bog plants. Then yesterday it was suspended in the water. If you lift a piece of lettuce out of the water, it looks like dirt particles floating everywhere off of it.

I turned my UV light on last night and it looks alot better. Nitrites are alot better today.

Yes, Yes, Yes. That sounds exactly like the brownish stuff I was talking to Robyn about, that settles in my biofilter. Now I can't find the post to give you the name of it. I was going to suggest looking it up. Sorry.

I dunno that it actually accumulates in the lettuce roots, but I can tell you for sure, moving the lettuce around in my bio filter is enough to stirr it up and cloud my water for a bit.

You may want to consider a bigger pump or additional filter media, or both. The more water movement the better, and faster results to clear water from unsettled sediment.

Floating plant roots will collect detritus and debris. It sounds like you have a lot of that which may result if you recently had an algae die off. The brown stuff, could it be dead algae? You can one by one dip the water lettuce and water hyacinth in a bucket and shake them off to clean some of the gunk off the roots and out of the pond. That dead algae or whatever it is should settle out of the water but it's better to remove at least some of it if you can either by cleaning the filter if it's in there or sucking some off the bottom.