What they’re trying to explain is that the water the fish was shipped in is full of nastiness (aka ammonia) from there being no filter to take out the fish poop and breathing waste. Put a plastic bag over your head, you’ll figure out pretty quick that as you breathe the air, you breathe out CO2, which is toxic to you. You’ll find it hard to breathe and after a while you’ll die. This is how the fish is in the bag. But when you dump that bag water into your acclimation bucket, all of that poisonous ammonia also goes into the bucket, and the fish is no better off. By adding water from your DT to raise the salinity during acclimation, you introduce clean water. However, the fish continues to breathe and produce waste the whole time. So the ammonia is still building up and causing damage the whole time the fish is in that original water. What the people above me are saying is fish don’t need to be drip acclimated. If you have a qt tank, you can fill it with water equal to the salinity of the bag the fish is in. You said that this fish came in water that was 1.020, so that would be the salinity you make the qt at. Float the bag until the temperatures match then net the fish and put it into qt, don’t dump all that nasty water in there with it. So now you’d have a fish in a qt tank at 1.020 and your DT is 1.025. So every day do a small water change and bump the salinity in the qt up by like 0.001. This way the fish acclimates, gets out of the ammonia water quickly, and you have a chance to really inspect it for parasites, diseases, injuries, or other such conditions. After the qt tank and the DT are the same salinity, just net the fish and throw it into your DT (assuming they’re the same temp) good luck!
