I have a box of API "aquarium salt" and I do not know why I have it but it fixed my snail problem. I had to add a decent amount of it... I think i added about 1 tsp per gallon? I was essentially trying to add enough to raise the sg a little. It took a couple of days but it totally killed all the snails, didn't harm my fish but took out a couple of the plants. I wasn't testing my water but I don't think it took out my bacteria, I didn't notice any distress in my fish that would have indicated spikes. Sg can be raised slightly without impact on the filter. They say it can be raised by .002 per week without hurting the bacteria, and I think years ago when i was transitioning a green spotted puffer from fresh to marine I'd do the full .002 raise at once, once a week, without hurting the bacteria. Obviously you have to be careful with what fish are in your tank using this method for snails, I just had a couple platies. I figured this was better than buying a snail killing chemical, though. It killed my anacharis, but anubias and java fern were fine.
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