I have x2 clown loaches in an established (6yr) 120L tank.
Weekly water changes alternating 25% and 50% every fortnight - never any problems with nitrogen cycle.
All water changes treated with Tetra AquaSafe, Tetra Easy Balance, and API Aquarium Salt.
But the larger Loach has...
With my tank I started with a male and 2 female Platies and a zebra loach.
Three weeks later, introduced a second zebra loach, 4 barbs and a sucker which I can't remember the specific name of now. I'll try and get a decent photo of him and the barbs to upload, but the barbs are a...