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Nitrites High - Why And What To Do?


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I have had a 20-gallon tank for 3 weeks, and I'm having trouble with nitrites. I have three 1-inch goldfish, plants in the tank and a few sticking out the top, a biofilter for 20-30 gal tank, bubbler, tank light, and purchased rock-like aquarium ornament and aquarium gravel. Ammonia is 0, Nitrate is 10, and Nitrites won't go down. I only keep them under 2.5 by doing 15%+ water changes every day. The pet store says it is because I have plants, but that doesn't tell me why the plants are causing the problem. They also tell me to stop changing anything, and let the fish "go" to get the tank cycled, but that isn't in my heart ? besides, that won't tell me why this is happening.

KH, right out of the tap, is zero, so I'm wondering if this is a problem, as it is related to the C02 the plants are taking up.

I did add 1 teaspoon of baking soda yesterday, and the KH went to 3, pH to 7.4. This morning before any changes, KH was 2, pH was 7.2. Nitrites were, of course 2.5+. Other chemistry -- Chlorine: 0 Iron: .05, CO2: 1, GH: 1, water temp 68 degrees F.

Today I added 4 tablespoons of dissolved aquarium salt, to TRY to keep the fish from being stressed until the nitrites go down. Even half a day after the latest 15% water change, nitrite is back up to 2.5, and I know from experience it will easily go to 3.0 before I freak out and change even more water, yet again.

The fish do NOT like the nitrite, and one does "flashing" which I assume is from irritation. I have lost and replaced two fish I believe from nitrite poisoning. One, I did initially "save" and put in a hospital tank overnight and he revived, but he was stunted and in 1 ? weeks, he was the second death. I have had 3-4 small goldfish in the tank since I started it up.

I add "Cycle" with every water change, in addition to treating the water for chlorine/chloramine. (Water is also left out overnight.)

As a test, I took a gallon of ("used") water out of the fish tank, added Cycle, and let it sit overnight with no fish, no plants, no rocks, no filtering, no aeration, nothing. There was no change in nitrites, still 2.5. When should I expect the bacteria to start to do their work? I am thinking that if nothing happens eventually, there really is something missing from my water to allow them to start working.

Maybe all of this is normal and you can just let me know. Or, is there something else I should be doing? Also, if the plants are really causing a problem, why? And why would they cease to be a problem after cycling?

Thank you for any help you can give, and for all the wonderful information available on this web site!

-- "lanternfish"

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  • Regular Member

Hello and welcome to Koko's! :)

It sounds like you are starting out alright but perhaps just lack a tiny bit of information....

If your tank is only 3 weeks along, it is still cycling - as you alluded to when you said you did not want to just "let it go" as the store fellow suggested. (Kudos to you for caring - That is WONDERFUL!!!! :D )

I am going to give you a link here to read about cycling..... read away. But also, here is cycling in a nutshell.

There are basically two types of beneficial bacteria (BB) that we attempt to cultivate in the tanks that make up the nitrogen cycle. The first type processes ammonia into nitrite. The second type processes nitrite into nitrate. Finally, you remove the nitrate from the water by either water changes or a combination of water changes and real plants that use the nitrates as food.

When cycling, the first type of BB develops first - and, as they process ammonia into nitrites, your ammonia levels will drop. The second type of BB is a bit more finicky - taking longer to appear and begin to process nitrites. Sometimes it can take a number of weeks for the second type of BB to develop a large enough population to process the nitrites.

The fish continue to create more ammonia - the first type of BB continue to process it into nitrites, but the nitrites go nowhere. Your readings of nitrates indicate that either you have some nitrates in your tap water (not all that unusual) or you have SOME BB that are processing SOME of the nitrites into nitrates - just not all of it on a daily basis.

You have done everything correctly - adding salt to 0.1% (1 tsp per gallon or 1 Tablespoon per 5 gallons) will help protect your fish's gills from nitrite injury - something that can result in lifelong problems. Changing your water EVERY day is, however, a necessary evil during this cycling stage if you have fish in the tank. You need to protect the fish. It is important to try to keep the nitrite levels at or below 0.50ppm - I prefer 0.25ppm - to protect the fish. This may mean LARGE water changes everyday.

To figure out how much water you need to change you calculate out what you have to dilute. IF you have a reading of 2.5ppm nitrites before a change you need to change out 80% of your water to get the reading to 0.5ppm. DO not be afraid of these changes - you are protecting your fish. The fish will continue to add ammonia and the ammonia will continue to be processed into nitrites - and your cycle will continue to grow.

IF your nitrates are indicating that you have the beginnings of a cycle going - nitrites beginning to be processed into nitrates - you are almost there. It will not be long, now. IF your nitrates are the result of tap water nitrates, you may have a bit longer to go.

It may seem a daunting task - and you may be ready to scream and throw in the towel - but believe me - IT DOES WORK. It is all worth it when the fish are swimming happily and you are enjoying your swimming jewels. :)

(One last question - when you say a "filter for a 20-30 gallon tank".....do you know what gph you have on your tank? Generally filters are rated for tropical needs - goldfish need more gph. The rule of thumb is AT LEAST ten times turnover an hour - or, for a 20 gallon tank, you should have at least 200gph. If your filter does not do this and you do not have LOADS of media for your BB to colonize you may have difficulty in getting sufficiant cycle built - or one that will not be able to grow with your fish as they get bigger.)

Oops - I forgot the links! :oops::blush:



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Oh thank you so much for your reply!

I have a filter rated at 150 gph, which you say is not enough. Should I add a second filter? I was thinking that would add more area for bacteria to live, but maybe two filters would be just too crazy or too noisy. ?? Or should I replace my current filter with a larger (maybe over 200 gph?) one?

I also read on this site about using cuttlebone for adding KH to the tank (I have KH=0) which would stabilize pH, and maybe it would give a good home for the bacteria as well?

One reads many different things about water changes. I plan to do an 80% water change tomorrow when the the fish and I wake up.

Thank you for the links, and I do appreciate your information.

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I started out the same way and I am still trying to cycle my tank after 80 some odd days! I have no KH/GH at all in my tap water, so I am going to have to use a buffer to try and get that up higher. hang in there, it will happen for you!!!!

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I have nitrites in one of my tanks for going on over 6 weeks now. I do 75% daily water changes, sometimes twice daily if needed. Even when you have everything correct (KH above 100, temp. above 75F, PH above 7.5, infrequent feedings, lots of media, lots of filtration, lots of aeration), it can still take forever.

I am sure it will happen for you eventually. Hang in there!

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