A few months ago my tank started smelling fishy, especially after water changes. I've had tanks for over 30 years and have never had this problem. I clean the lip of the tank regularly so it's not that.
My nitrates have been elevated, going to about 50 at times. They come down after water changes. My other levels are normal.
Why would it smell AFTER the water changes? My three clown loaches just got Velvet and died. When I took them out to quarantine them they STUNK!!!! I increased the temp to 80 and all the other fish are fine. The nitrates are now down to about 10ppm.
Would sick fish cause the whole tank to smell? Do you think the loaches had been sick for a while? There was no sign until last week.
I do water changes twice a week (50%) because I have a high bio load. I use a conditioner for tap water.
70gallon filters and a large airstone.
-Finnex light (I've noticed water has gotten inside the light)
-Many pieces of 15 year old Mopani wood
-Five anubius plants
-3 clown loaches (about 8 years old) now dead
-3 parrot fish (about 3 years old)
-8 giant danios
Thanks for any advice.