Nitrite and nitrate spike

[Tomislav Lukić]

Hi guys,
I need help.
So I have a 20 gallon heavily planted tank that’s been running for about 6 months. Until now everything was perfectly fine, nitrite 0, nitrates between 10-25. I can't test for ammonia because none of the pet stores around here have any kind of ammonia tests for some reason.
Yesterday I tested my water like I always do, and saw a huge nitrite and nitrate spike. Nitrites were between 2 and 5 ppm, and nitrates between 25 and 50. So I decided to do a 50% water change and dump in a whole bottle of Tetra SafeStart and haven't fed my fish in 24 hours just in case. And it was fine for a while but today I tested the water again and I have the same results as yesterday. I have no idea what's going on. I don't have any dead fish or plants in the tank, I do weekly water changes, vacuum the gravel, clean the tank and trim the plants regularly. I mean, I've been keeping fish for years and I know what I'm supposed to do but this is the first time something like this happened to me.

Current tank inhabitants are: 1 male betta, 1 siamese algae eater, 2 female mollies, 6 cardinal tetras and 3 dwarf corys.

Current tank parameters:
nitrates between 25 and 50
nitrites between 2 and 5
GH around 8°d
KH around 6 °d
pH between 6,8 and 7,2
Temperature: 26°C (78°F)

Equipment:
Waldbeck clearflow canister filter with fluval coarse and fine foam, fluvar filter floss and fluval biomax bio rings, flow rate around 200 gallons per hour
Tetra APS air pump
Aquael Leddy Retrofit Sunny 10W light.

I know the tank might be a little bit overstocked but I never had problems until now. I'm not overfeeding my fish, they eat all the food I give them so there's no leftover food in the tank.

 

[Colin_T]

Hi and welcome to the forum

When was the last time you cleaned the filter and how do you clean it?

Just do a 75% water change and gravel clean the substrate every day until the levels are back down to 0. Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

 

[seangee]

Test your tap water too.
Also worth testing your tank again immediately after the W/C. Once its had a good stir if you changed 50% you should only have 50% as much NO2 and NO3. If that's not the case it may be possible your test reagents have gone off.

 

[Tomislav Lukić]

Hi and welcome to the forum

When was the last time you cleaned the filter and how do you clean it?

Just do a 75% water change and gravel clean the substrate every day until the levels are back down to 0. Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

I cleaned the filter a few days ago. Probably like 5 days ago. I clean it in tank water, just squeezed it a couple of times until all the gunk came out.
I did another water change today and I’ll check the parameters later today. I’ll try doing water changes every day until everything looks ok. I just hope I won’t stress the fish too much. I don’t have another tank to put them in. I only have a 60 gallon cichlid tank and a small 10 gallon tank that I use for quarantine.

 

[Tomislav Lukić]

Test your tap water too.
Also worth testing your tank again immediately after the W/C. Once its had a good stir if you changed 50% you should only have 50% as much NO2 and NO3. If that's not the case it may be possible your test reagents have gone off.

Tap water is fine, no nitrites or nitrates. And the reagents are fine too, I use them on my other tanks and they’re showing good results on them.
After the water change the concentration drops by 50% but in a few hours it just spikes up again.

 

[PheonixKingZ]

Usually when you do water changes, you don’t get a spike in parameters. Does anyone else find that weird?

 

[seangee]

Tap water is fine, no nitrites or nitrates. And the reagents are fine too, I use them on my other tanks and they’re showing good results on them.
After the water change the concentration drops by 50% but in a few hours it just spikes up again.

Ok - sounds like your tank is partially cycled (or uncycled if you prefer).
Keep testing for nitrites daily and continue the water changes until they drop to zero. No point in testing nitrates until they do because the test includes nitrites in your nitrate reading.
Double check there is nothing decaying in the tank or the filter, but if you are getting nitrites that quickly you know that you have the bacteria in place to convert ammonia so you are already part of the way there and not having an ammonia test is not a big deal.

What is concerning is that you have nitrites at all if it is heavily planted. Do you have a photo. The plants should deal with the ammonia without producing nitrite even if the filter has failed.

Just FWIW it doesn't sound like you are overstocked but your water is not hard enough for mollies (but that's not what is causing your problem).