Last winter I has an ich infestation in my 110 gallon home aquarium, so I thought I would try using pond salt to help the fish out. The odd problem was I wound up causing the Fluval filter's bacteria to die off. I wound up crashing the aquarium since I introduced the salt too quickly into the system. What should have taken days, I did in a few hours and the biological filter did not like it. I lost many fish from this over a short period, and made matters worse.
I never had heard of this problem before, but the evidence in my tests said my filter did die off. Lots of water changing and re-starting the filter finally settled things down, but it was a mess.
So be careful with your salts and keep the level relatively consistent.
Yeah those little critters are sensitive! They don't like drastic salinity, temperature or lighting changes! Interesting thing is if you can hang on to them year around for a few years they become more mature and durable. Used to start the school bacteria over again each year. Took too long. Now I bring the media home at the end of the school year and feed it ammonia or incorporate it in existing systems. Then I schlup it back when school starts again.
On the other hand I have placed up to 4 cubic feet of the plastic media in a large tub without water for a couple of days because I was moving some from the schools, and didn't have a moving bed tank ready, and they were fine when I cranked them back up with water, air, and a little ammonia for food.
