Nitrites in the tap water

[kclarke]

Hi,

I have had my tank set up now for 2 weeks, so I am still waiting for it to become stable. As I have previously mentioned it is a 4 foot, etc and I am using an undergravel filter as well as a filter that fits on the inside of the tank. I have put in a couple of cat fish (very pretty ones) and they are going fine. But of course I want everything perfect for the Discus that will be living there.

I have been doing a few partial water changes to keep the nitrites down, and I did one tonight. The nitrites read .25. After I changed the water it still read approx the same so I tested the tap water and it reads .25. I have been told that Cockatoo have decided to add ammonia to the water (for whatever reason) and even though I haven't detected any ammonia, what about the nitrites?

The big question is: Is this amount harmful to both fish and humans or is it negligable and if the former how to I counteract it?

Any information will be helpful.

Thank you

[Ira]

If that's .25 PPM then it's nothing to worry about. Once your tank gets cycled it should be able to handle that little bit of extra nitrite and convert it into nitrate pretty quick anyway.

[Warren]

If you are going to keep Discus, your pH will be less than 7. In this case there will be no ammonia in you tank, only ammonium. Ammonia is toxic to fish, but ammonium is not. As Ira states, you filter will take care of the rest once it is mature. I would expect the nitrite bacteria to be starting to form about now. Over the next week you should see the nitrites drop and the nitrates start to rise. Once the nitrite has fallen to 0 your tank is ready. I would put in a few more other fish at this time. This will increase the load on the filter system and make it stronger. If you suddenly introduce 6-8 discus from virtually empty, the filter will not be able to cope and it will go through another nitrogen cycle. This can be harmful or even fatal for the fish.

You could probably add a bit of Cycle to your tank about now too. This will help to kick-start the nitrite to nitrate conversion.

[Ira]

Ammonium IS toxic to fish. It's something like 1/10th as toxic as ammonia, though so if your PH is low it's not a huge worry. If I remember right the PH controls the ratio of ammonium to ammonia in the tank. Below something like 6 it's basically all ammonium, above 8ish it's all ammonia, at 7 it's about 50/50.

Disclaimer: This is vaguely remembered and definitely not exact to the details, but is at least the right idea. I think.

[kclarke]

Hi Warren & Ira,

Thanks for that bit of info, I won't panic now. I was thinking of getting a couple of the Discus next week, which is 3 weeks after set-up. I will wait if need be.

I'm not going to get all the Discus in at once. What I was going to do was put 2 in from one aquarium supplier, getting to know them and making sure everything was OK and then getting another couple from a different shop a couple of weeks later and another 2 somewhere else. All the same type but from different parents. So that hopefully they will pick their own mates and have a bigger gene pool. Does this sound about right?

I do want to breed them when they grow and hopefully out of 6 I will get at least one male and female. I know there are no guarantees but we will see.

In the meantime I will just enjoy them for being them.

[kclarke]

PS: The PH is set at between 6.6 to 6.8 is this about right or should it go lower?

[Warren]

If you are going to only put in 2 discus to start with, keep an eye on them. They sometimes bully each other to the extent that one will die. If this is happening, you may have to temporarily fit a divider between them until you get more. Once you have 6 the fighting is usually distibuted between them enough to sort out problems.