GH causing death?

[Cattrah]

Just call me the fish killer :-( I've done everything to the letter and all my fish have died in less than 48 hours (1 platy, 1 swordtail, 1 guppy...3 ghost shrimp are thriving, eating, and swimming fine). Took my water in to LFS and had them test it cause I figured I MUST be reading my tests wrong, but no, their tests showed the same thing mine did.

0 Ammonia
0 Nitrites
5 Nitrates
Ph 7.8
GH 40

I know the water in my tank is soft. I have a water softener and have been using half softened water and half very hard water. Temperature has been steady 77 degrees (checked with an infrared thermometer which confirmed my sticky tank thermometer was also correct). I feel like I've done everything I was supposed to. The whole reason I did a fishless cycle was to avoid the unnecessary loss of life.

I'm so distraught, everything I've read hardly mentions hardness or that it's not a big deal and fish adapt but I can't think of anything else that caused the fish to go downhill so fast. The LFS water is very hard (local unsoftened water) and mine is softer by more than half. I guess the fish couldn't adapt to the softer water? Went and got another platy and guppy from a different store, changed 50% of the water replacing it only with unsoftened hard water. It brought the hardness up some. I'm hoping I don't wake up to more dead fish :-( Any ideas?

 

[Fishperson]

I doubt that every single one of your fish would die due to soft water. How did you acclimate them? What are you testing with? Did you check the fish for any signs of disease?

 

[Cattrah]

API liquid test for Ammonia and API test strips for the rest. I know test strips can be inaccurate which is why I took the water in for testing but the results were the same.

I acclimated them over an hour and a half, removing 1/4 cup or less of water from the floating bag and adding the equivalent tank water every 10 minutes.

I think the platy was on his way out, he was lethargic from the shop. The guppy and swordtail were vigorous swimmers when they got into the tank, playing and checking everything out. Next morning, platy was dead, guppy and swordtail still seemed vigorous and they ate very healthily, that afternoon swordtail seemed less vigorous, but I didn't suspect sick. This morning swordtail was dead, guppy was clearly less vigorous, wasn't swimming through the current from the filter very well. This afternoon he is dead. Only the platy seemed sick when I got him, the other two looked and acted very healthy.

The new platy and guppy I put in this afternoon are very vigorous, swimming easily through the currents, uninterested in eating though, I figure they're just busy checking out the new digs.

I guess because a potential hardness shock is so uncommon maybe no one really knows that it can be killer...?

 

[Fishperson]

Hmmm, maybe. It could just be a fluke. I've gotten "bad" fish before, that just seem doomed to die. It happens a lot with neons, otos, and sometimes dwarf cichlids. Are you sure there wasn't any disease? Maybe try drip acclimation next time?