Overstocking and nitrites

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Kilgore

Aquarium Advice Activist
Joined
Feb 13, 2006
Messages
147
Location
Portland, OR
Hello,

I currently have a fairly overstocked tank which I plan to upgrade soon, but it may be up to a month before I can move everyone to the bigger tank. I am concerned because I have been getting nitrite readings for about 1 1/2 weeks now and can't seem to get rid of them. The tank had completed its cycle thanks to BioSpira prior to adding the new fish, so this is likely a second "mini-cycle."

This a heavily planted 25 gallon tank with an Eheim Ecco filter that is currently housing 33 1 - 2" fish (tetras, cories, otos, and hatchets). None are full-grown except for otos. I also have another tank going but it is being medicated for a parasitic infestation thanks to guppies from LFS and so none can be moved in there yet.

In the meantime, I have been doing water changes of about 15-20% every few days. I have been monitoring water and saw no ammonia spike, probably thanks to plants, but the nitrites, although they are decreasing, are definitely still present.

Last week, nitrite readings were 0.5 ppm (according to Jungle Quick Dip Test Strips). Today, the amount is no longer registering on the strips which means they have fallen below 0.5, but according to my Seachem test kit they are still about 0.2 -0.40 (hard to tell exactly).

Now to my question (finally, you say): exactly how long term are the long-term negative effects of nitrites, assuming fish are in good health? If it takes another week before nitrites go away, will that be too long? What else can I do? I have been using Amquel + but it is a dangerous game considering that I have very low KH, and don't want to cause a pH crash. Furthermore, for all I know Amquel + could prolong the cycle - it says it leaves the ammonia available for bacteria but doesn't mention how it affects the nitrite cycling.

Any words of advice, encouragement, or other help will be greatly appreciated. Thanks!
 
how long term are the long-term negative effects of nitrites, assuming fish are in good health?

OK, if you can keep the nitrIte's at or below 0.5ppm, you will be fine. Since you have a lot of plants the oxygen level in the tank should be adequate. Salt added to the tank makes the nitrIte less toxic, however I would be worried about the fish (especially the cory's and Oto's). NitrIte acts in fish like carbon monoxide acts in humans. It competes for the oxygen binding sites in the fish's blood, and is IRreversible. What this means is that once the nitrIte attacks and alters the blood cell, it can no longer transport oxygen. When enough of the cells get damaged, the fish will suffocate.

Now the good news. Unlike burns from high ammonia levels, the blood cells in the fish's body will be replaced with new blood cells after a period of time (I have no idea about the timespan in fish, but I believe humans are about 120days, so I would imagine fish are much shorter). Long term effects of nitrIte poisoning are not good, but again your tank is in the process of cycling so after its cycled your nitrIte will be zero. Here's a good excerpt from a website:

Fish that are exposed to even low levels of nitrite for long periods of time suffer damage to their immune system and are prone to secondary diseases, such as ich, fin rot, and bacterial infections. As methemoglobin levels increase damage occurs to the liver, gills and blood cells. If untreated, affected fish eventually die from lack of oxygen, and/or secondary diseases.

Long story short: You shouldn't see any permanent damage IF you keep the levels at or below 0.5ppm during your cycle.

HTH

justin
 
Thanks for the very useful info, I just wasn't sure how "long periods of time" should be defined. I mean, that could be two weeks, two months, or one year. :)

The nitrites are definitely below 0.5 ppm right now and I have high hopes that they will continue to decline, in spite of the tank being overstocked. I have not reused the Amquel + due to its pH lowering effect in my tank (went from about 6.8 to 6.6 in two days), and also because I am afraid it will interfere with the bacteria that break down nitrites.

I will leave my air stone on during the day as well as the night until the nitrite is no longer detectable. The plants will be ok with less CO2 for that brief period of time. Guess I will wait to start up my CO2 injector also. :)
 
Sounds to me like you are at the tail end of your cycle, and it should only be a short time before you never see ammonia or nitrIte again. The one nice thing about being overstocked in a heavily planted tank is that you shouldn't have a need for adding nitrAte into the tank. I'm still on the other side with to much nitrAte production and not enough plants, but I figure when the plants continue to grow they will absorb more nitrAte letting me get a bit more lazy with the water changes (my tap water has ~10ppm nitrAte already so I have to do larger PWC's weekly than most to stay under 30ppm).

I just started my DIY CO2 4 days ago and can definately say its great. With your current pH however and your low KH, you will DEFINATELY need to do some serious KH buffering (and probably increasing the pH as well permanently through some other means). I started at about pH 7.0-7.2 and after adding CO2, it drops to ~6.2 during the night. I'm hoping that with my plants growing better, they will be able to use more of the CO2 so that my pH doesn't drop quite as far. I've also been adding some baking soda to bump up my KH slowly. I don't have any test kits for plant related things yet so I'm kind of flying blind, but so far no big problems.
 
I was thinking about doing a little crushed coral in my filter but it is such a balancing act because I've never used CO2 before, and my fish are mostly sensitive species who prefer soft, acidic water. I recently killed 5 out of 7 guppy fry using Ammo-Lock which caused the pH to crash from 7.4 to 6.0! I can't believe yours survived the overnight dip - they must be tough fish.

If that happened with this tank I think I'd jump out the window (kidding)! But seriously, imagine killing an entire tank of fish. That's my nightmare. I want my plants to thrive but Portland's water just has no kH. I need to be able to raise it without raising my pH too much - I realize the CO2 will counter that effect by lowering the pH but I really don't want to rely on C02 to stabilize my pH. I mean, what if I want to stop using it or run out ingredients for a little while?

Maybe it's time for another thread.
 
Something that you need to keep in mind is that swings in PH caused by CO2 aren't anywhere near as hard on fish as PH swings tied to changes in KH. So it really isn't surprising that 7Enigma's fish survived the CO2 induced PH swing with flying colors. I really think that it is the changing KH that harms fish and not PH. It's just that KH and PH usually rise and fall together and more people have PH test kits.

Using Crushed Coral or Coral Pieces to buffer the KH is pretty easy, but inexact. If you take that route add small amounts and test the next day to determine if more is necessary. Periodic testing (which you should be doing to keep an eye on your CO2 anyway) will let you know when it's time to add a little more as the existing Crushed Coral gets disolved by your water. Baking Soda is another method that can be used with much more precision, but requires dosing the new water with each water change. Since you have such sensitive fish, whichever method you choose, just remember to take it slow so that your fish have a chance to aclimate to the new KH. Perhaps even take a few weeks to adjust your water to where you want it in the end.
 
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