i bought a 45 gallon aquarium from petsmart and let it cycle for about 3 weeks before putting any fish in it. (its been running a Fluval Aquaclear 30-50G filter, heater set to 75F and had a gravel substrate since day one) first i added 3 twinbar platys. a week later 5 cherry barbs. then a bristlnose pleco another week later, and finally i moved my favorite (rainbow Shark) out of my girlfriends 10G tank into my 45G. All the fish have been together with no problems until 4/6. On sunday i decided to change my substrate to Sand because i think it has a more natural look to go with my decorations in the tank. so i went to petco and grabbed 2x 20LB bags of sand. Ghost shrimp caught my eye so i grabbed three of those for my tank too. I siphoned out half the water into an ice chest, put my fish in it (the first cherry barb i got in the net immediately died. brought the net out of the water and it just stopped moving. i put it back in the tank to see what it would do and it didnt move for an hour. i assumed the worst and euthanized it by throwing it in a pot of boiling water)
with the filter and began changing my substrate (no extra tank for them to be in) scooped out the gravel and slowly added the sand. once it settled i put the fish and water back in the tank. about an hour after they were in it i noticed white spots on the cherry barbs. since i only had my 10G for about 2 months im still relatively new and thought nothing of it. i thought it was just sand cause the new sand was white. later that night one cherry barb died. again, still new
Monday i noticed my rainbow shark rubbing on stuff but didn't think much of it. and now, Wednesday evening, i came home to the last three cherry barbs dead, one orange and black molly dead, one twin bar barely alive, and white spots on every other fish. i looked it up and immediately went out and bought API super Ick Cure. so at this point ive assumed all my fish are a lost cause. 3x twinbars, 1x orange and black molly, 1x Rainbow Shark, 1x bristlenose pleco remain.
my question is did i somehow cause this outbreak? could the substrate swap have caused it? i cleaned the sand reeeeally good before putting it in. also, is there a chance my remaining fish will make it? due to my newness i didn't see that there was an obvious problem and have already lost 6 fish.
i apologize for the length but i want to know if anything i did could have caused this and what i should do differently for future cases. if i missed any important information please let me know.