I'm hoping you can provide me with some help and guidance. We have an 89 litre bout tank. It's about three years old and has been cycled for about the same time.
The nitrate levels have been stable at 20 for months. We've now had a sudden spike.
I did a water change on Saturday (usually do a third water change every 2-3weeks) and tested the water rates a few hours after the change. Nitrates were down low.
Then last night I noticed the fish were clamping fins. Took a water test last night and nitrate was at 80!
Why? No new fish added recently.
I guess daily water changes will bring it down?