Advice for bloated (?) zebra danios
Hello! I have been dealing with a problem that only seems to affect my female zebra danios. The past 2 fish I have lost since setting this tank up have been female zebras, seemingly from the same problem. They look normal when I buy them, but they gradually bloat until they get dropsy. I have had to euthanize 2 due to pineconing and swim bladder dysfunction. I have 3 left (2 females, 1 male). The males are never affected, and neither are the females of my other species. I have tried feeding them less (one pinch a day) and tried their spawning method (2-3° cooler 25% water change at dawn separated from main tank with males) with no results. I really hate to see them progressively get worse and have no idea how to help or what might be causing it. Any advice would be great!
Parameters:
20 gallon tank, activated carbon filter, air bubbler, live plants, medium-sized pebble substrate
Tankmates: 4 brilliant rasboras, 3 ember tetras, 3 sparkling gouramis, and 50-ish neocaridina shrimp
72° (dechlorinated) water
pics of water test, danios, and their food below. Last pic is a male danio for comparison.