Sorry, this is going to be long winded but the more info the better right?
I had a 55 gallon tropical community tank, established for over 1 year. Never really had problems or issues with the tank or the fish. I recently bought a brand new 120 gallon tank. I transferred all of the gravel from the 55 gallon and another 47 gallon tank that I had (I sold the 47 G to buy the 120 G) making sure that it was never rinsed in tap water and never dried out to preserve the bacteria. I also moved the Aqua Clear 70 G filters (x2) from both the 55 gallon and the 47 gallon and put them on the 120 gallon. I used as much of the water from the old 55 gallon tank as I could since it was a healthy tank but I did end up having to top it off about 50% with new, conditioned water (I use Seachem Prime) to fill it up. I don't use any other chemicals.
I had 6 platy fish, 4 mollies, 20 neon tetras, 4 red eye teras, 4 small cory catfish, 6 zebra danios, and 1
betta. I transferred them over to the new tank. I added two clown loaches after the transfer. The clown loaches, cories and danios have been fine. The platies and mollies have been fin clamped and hover by the heater, the red eyes are not schooling anymore and hide most of the time. They weren't really active before but more so than they are now. The neons seem really distraught and don't school like they used to. I have fished out 5 dead neon tetras since the transfer on Sunday. They aren't the hardiest of fish so I thought it was sheer stress of the move.
Yesterday morning I turned on the tank lights and began feeding as usual. I noticed that my favorite fish and one of my hardiest, my bright purple betta, did not come out of his cave as he always has everyday since I bought him over a year ago. I lifted up his cave and he rolled out listless. He was pale white, had lost almost all of his coloring, he had a couple of patches of yellowish raised coloring randomly on his body, but not at all hairy like fungus though, and he looked extremely swollen all over. He was not like that at all when I turned off the lights the night before. I immediately transferred him to a 10 gallon quarantine that I keep running and ready under the main 120 gallon tank, mostly for quarantine of new fish. I added 1 tsp. per 5 gallons of aquarium salt (don't keep salt in the main tank because of the tetras but the mollies have always been fine without it), the recommended Melafix and some Minocycline. He was dead this morning.
I tested my tank water. I use liquid drop kit for everything except KH &
GH because all the store had was strips for those last time I was there. I always keep an eye on this but apparently I underestimated what 50% new water would do to my new tank despite thinking I was doing everything as I should. My temp is always 77 consistently. My
pH is always 7.4. It comes out of the tap that way and I have never seen a change in it. My
ammonia and nitrites are always 0. My nitrates had been about 30
PPM before the change but they went down to 7.5 ppm with the change. My KH and GH dropped to almost nothing. GH is now 30 and KH is now 40 as opposed to GH being 120 before and KH being 60 before. I don't know much about GH and KH or how to change it without dumping a bunch of junk in my tank and I don't want to kill anymore fish but I suspect this is certainly the problem since it's the only levels that's so drastically different. How can I safely and effectively help my fish?
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