nitrate spike

Question
Hi I have a coldwater goldfish tank 110lit set up 18 months ago. The last two weeks I have been getting nitrate spikes, have done water changes the fish have been on same food, no new plants or fish added . three fish in tank, black moor, lionhead , bubble eye . if i add salt does this help if so how much ? thanks

Answer
Hi Rob
I just want to make sure, you are talking about nitrAtes and not nitrItes correct?  Salt won't do anything with nitrates, but if it is nitrites, 1 tablespoon per 5 US gallons will help the fish to deal better with the nitrites.  And, the salt won't get rid of nitrites.  Just want to clarify that, sometimes it can get confusing when dealing with those two.

What exactly are your nitrates reading?  You want to aim to keep them under 20 ppm.  If it's nitrites you meant, then those you want to keep at 0 ppm.  

Now, if it is nitrates, the most likely problem/cause is not enough water changes being performed.  I recommend doing a 25% water change/gravel vacuum weekly-for a normal stocked tank.  For your tank size though, with 3 fancy goldfish, it's a bit overstocked.  For fancy goldfish, it's recommended to have 15 gallons per fancy goldfish, so 2 would be ideal for your tank size.  For the 3, ideally you would want 170 litres.  

I would recommend doing two weekly water changes/gravel vacuums of 25%, and stick with that schedule.  If the nitrates are really high over 20 ppm, then do daily water changes till they lower, then go on the twice a week schedule to maintain those levels.

Be sure you're only feeding the fish once a day, and only what they'll eat in a few minutes.  Net out any food that's not eaten.

What kind of filter are you using?  If it's an undergravel filter, those aren't good. They have a tendency to trap uneaten food and waste under the plates, which can lead to water quality issues like you're seeing.  If you do have one of those types of filters, I would recommend removing it, and using a power filter that hangs on the back of the tank.  

Another possibility as well, if you're on well water.  If that's the case, try doing a test on your tap water.  With well water, sometimes fertilizer/run off can get into the water, which can cause your nitrate levels to go up, occasionally high.  It's usually not an issue with a public water supply though.  

Now, if it is nitrites you are seeing, then something happened to the beneficial bacteria in the tank, and it's going through a mini cycle.  If that's the case, then daily water changes will need to be done until it finishes the mini cycle, and 1 tablespoon of salt per 5 US gallons should be added.  Nitrites inhibit the fish's ability to absorb oxygen into their blood stream, and the salt counter acts that.  

Think that covers everything.  Let me know if you have more questions and good luck.

Christy