Sailfin Mollys, Salt And My Other Fish

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My tank is mostly tetra,s, a few barbs, rainbow fish and a silver shark, a few weeks ago i added a couple of sail fin mollys which were fine for a while now they just hang around the botton, not really swimming much, i hear that adding salt can help them, although i don,t want to risk hurting my other fish for the sake of keeping the these two happy, is it harmful? and is it the sort of salt i would put on my chips or special stuff, also my rainbow fish bug the hell out of them for some reason, chasing them and rubbing up against them all the time, i have no idea why. Should i just take back to the shop.

 

[tenohfive]

Whats your water stats like?

 

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To be honest, i don,t know i have not tested it, but i water change about %10 on weds and sundays, and my other fish do great, been running this tank for about four months and have not lost anything, well there was one harlyquinn that decided to jump out when i was cleaning the tank, i found it on the floor about three days later. I suppose i should mention that i have been running the set up with no light (messed around by a shop that kept saying they had ordered me a lid ) but hopfully i am getting that sorted in a few days time.