Sudden Molly deaths!

[Grounderfree]

Hi all

i recently just got my first tank in September. I had comets in it for the longest time. About a month ago I added 6 mollies And 3 corys. on the 26th I removed the comets (as they were too large) and I’ve had 2 mollies die on me! I also added some more water as the water was getting low but I treated it with conditioner before adding.
I test my water each week and have 0 Ammonia and nitrite, about 25ppm nitrate, 150ppm GH, and about 80ppm KH (this is my only value that variates) with about 7-7.5 pH. From what I understand these are ok ranges.

what is going on? Could I kill them by overfeeding? Adding too much water conditioner? I don't know why it’s been a month and they are just dying now

 

[mrsjoannh13]

The nitrates might be a little high. Are you doing water changes with gravel vac or just adding new water? Is the tank heated? What is the tank size?

 

[Callisto405]

Sounds like you poisoned your fish when you added water. What brand of conditioner did you use? Is your tap water treated with chlorine or chloramine?

 

[Colin_T]

Any chance of a picture and short 60 second video of the fish?
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The GH is a bit low for mollies who prefer it around 250ppm. However, that is unlikely to be the main issue.

 

[Grounderfree]

The nitrates might be a little high. Are you doing water changes with gravel vac or just adding new water? Is the tank heated? What is the tank size?

Yes I vacuum the gravel when I do the change. Just didn’t add enough last time