Unexpected nitrite spike

[frosty9]

Just tested my water and got a nitrite reading of 1.0 ppm out of nowhere. Tank is a 20 gallon with 6 Neon Tetras, 4 Corydoras, and a Betta. Did a 25% water change yesterday, filter is a HOB AquaClear 30. Any ideas what's up?

[bites]

That's sketchy. Did you add any new fish or mess with the filter media recently? Even moving stuff around can crash your cycle. Also, what's your ammonia reading? If it's zero, your bacteria might be struggling to convert nitrite.

[deepfin]

I've had this happen after overfeeding. How much are you feeding? Those Corys can be greedy, and leftover food'll spike nitrites fast. Try cutting back to once a day for a bit.

[knight]

That's sketchy. Did you add any new fish or mess with the filter media recently? Even moving stuff around can crash your cycle. Also, what's your ammonia reading? If it's zero, your bacteria might be struggling to convert nitrite.

Yep, second this. Check ammonia first. If it's high too, your cycle's fully crashed. If not, just a partial hiccup. Either way, daily small water changes till it's stable.

[thinfin]

Gonna throw in that substrate vacuuming might help. Corys stir up gunk, and if you've got detritus buried, it'll leach nitrites. Also, what's your pH? Lower pH slows nitrite conversion, so that could be part of it.

[frosty9]

Ammonia's at 0, pH is 7.2. Didn't touch the filter, but I did add a new piece of driftwood last week. Could that be the culprit?

[bites]

Driftwood can sometimes cause a mini-cycle if it's leaching organics. Not usually enough to spike nitrites this high, though. You dosing with Prime or similar? It'll detoxify nitrites temporarily while you figure it out.

[chloe]

I'd test your tap water too. Sometimes municipalities change treatments, and you get surprises. Happened to me once with chloramine.

[deepfin]

Ammonia's at 0, pH is 7.2. Didn't touch the filter, but I did add a new piece of driftwood last week. Could that be the culprit?

Maybe if it wasn't pre-soaked. Rotting wood can suck up oxygen and mess with bacteria. But like bites said, Prime's your friend here.

[knight]

If you're using tap, check for nitrites there. Some wells have 'em. Also, how old are your test kits? Expired reagents give false readings.