Tcpd28, generally nitrite levels > 0.25 ppm can be potentially harmful to your fish. Possible causes are either overfeeding and/or underfiltration.

Short term, I would do small partial water changes to bring the NO2-N to an acceptable level. Also, reduce feeding and increase aeration.

What size pond? How old? What type/size bio-filtration?

8x8x3. Have both mechanical & bio filter falls. Have bottom drain. 4 koi, 4 shabunkin, 4 goldfish. I have anacharis, lilies and parrots feather. That's about it. I just finished it last weekend. This is the 1st week that it's been running. I feed the fish twice a day. maybe I need to cut that down. Thanks for responding!

Yup, you should cut down the feeding to about every 2 days so that the biological filter can slowly establish to the bioload.

If I cut down the feeding that will take care of the Nitrite problem?? Won't they be hungry?? I did add all those fish at one time too. I now know better.

Yes, you added too many fish too soon. It will take a couple of weeks for your filters to start processing nitrites into nitrates. As one emergency measure you might think about adding lots of water hyacinths. They will come with colonies of de-nitrifying bacteria on the roots. The surface area of the roots of a water hyacinth is pretty large, and it is all covered with bacteria. The hyacinths will also use the nitrites directly as a source of nitrogen, and they love their nitrogen.

I would also STOP feeding the fish for at least a week, maybe two. They are a lot more likely to die of the nitrites than they are to die of starvation.

Something doesn't make a lot of sense. This pond is less than a week old so I don't think you have bacteria in there yet to convert ammonia to nitrites yet. So unless you put a working filter on this pond or debri from a working filter the nitrites are not coming from the pond. So the first thing that I would check is are there nitrites in the water that you used to fill this pond? If not than can run off be getting into the pond. Since you didn't say anything about ammonia levels I assume you haven't built up enough ammonia for your test kit to detect it. You are headed for a problem if you continue to feed at the rate you are. I would switch the fish off regular food and put them on Cheerios as that will cut down the amount of the ammonia the fish will produce. Plan on having to do water changes to keep the levels at a point that is safe for the fish. That will be determined by the PH of the water. Also put some salt in the water to protect the fish from the nitrites. I would use at least .05% or higher which is .5 pounds per hundred gallons of water.
Mike

Mike, The anacharis, lilies and parrots feather all have surface area that presumably were all inhabited by de-nitrifying bacteria when they were put into the pond. This could account for the nitrite production.

I don't have much experience with salt (I add a couple of pounds a year to my 2,500 gallons), so I don't know what effect the salt level you are calling for will have on the plants, but I am concerned that it might cause harm to the plants. Since they are probably the only bacteria covered surfaces at the moment, I wouldn't suggest harming them.

Testing for ammonia makes a lot of sense.

Thankyou all for responding. My Nitrites are testing less than .03 today. I added 24 water hyacinths today and more anacharis. I also put some more plants in. I added 3 more water lilies and some other things. My water today is cloudy and starting to turn green. I stopped feeding the guys although they were following me around the pond today begging LOL. I'm going to add some water today. Unfortunately my only water supply is my hose and it's city water. I do put in the dechlorinator though. Any thoughts on any of this?? =)) How often would you suggest cleaning out my skimmer filter/basket? How about my bio filter?? I have lava rock as media in it as well as the scratchy pad thing it came with.

The last thing you want to do now is clean any filters. Unless they are totally clogged up and non-functioning don't clean them. Any surface in your pond functions as a bio-filter as soon as it gets covered with bacteria. Your filters are part of this surface. Cleaning removes the bio-film. Bacteria are your friends.

Go ahead and clean the skimmer as this is not meant to be a biological filter but a mechicanal filter. The bacterial that converts nitrite to nitrate is very fragile and I would doubt that it would survive on any plant that you were to buy. Salt for a limited time will protect the fish from nitrite. At the levels that I suggested that salt should be added would hurt any of the plants. It might slow the growth of the hyacinths but I doubt that if the gallonage is correct. As far as the nitrite levels dropping I would say that it is test error.
Mike

"My Nitrites are testing less than .03 today."

Hmmmmmm......... What test kit are you using that gives THAT kinda accuracy??? My "logic" tells me that it would be impossible for any amount of plants to reduce nitrites from 0.5 ppm to practically 0 on the same day. I believe you probably meant 0.30 instead of 0.03. If so, your fish are not out of the proverbial woods yet.

Feeding 12 fish twice a day in a week old ~1000 gallon pond with an unestablished bio-filter is a formula for disaster, IMHO. As was already mentioned, I have definitely seen fish die of nitrites but have yet to see a fish die of starvation in a well-stocked pond.

That might be what it was. I used the Tetra Nitrite Test Kit. I stopped feeding them and I did add a ton of plants yesterday along with all those hyacinths. Thank you all who responded. I will clean the skimmer filter/basket only.