Rotten egg smell from fresh water tank

Question
Hi there,
Here is my unfortunate situation:
I bought two betas (females) Thelma, and Louise.  I have them in two separate tanks.  Louise has been doing fine, with what seems to be normal water.  Thelma however- her water was very, VERY slimy, within 24 hours of a water change.  I went to the store where I purchased them from.   I got some great advice and purchased two snails, one for each tank.  So along with cleaning thoroughly the contents in Thelma's tank I added treated water that the store gave to me to try, a snail, and very clean contents.  
I've noticed over the past couple of days that Thelma's water is VERY cloudy, and Louise's water is partially cloudy. Seemed I've nicked the slime problem but have a acquired another. I thought perhaps this had something to do with the addition of the snails?   So, I went today to purchases de-clouding liquid for my girls, as the help at the store said it's just unsettled water,  and some underwater plants for my snails.  Come home to see that not only is Thelma's water outrageously cloudy but also smells like rotten eggs.  Ugh!
I want happy, healthy fish, but it seems like I am hitting curve balls all over the place as far as water quality goes... Any suggestions would be greatly appreciated.
Thanks very much,
Lesley, Thelma and Louise.

Answer
Dear Lesley,
If it's a rotten egg smell you have decaying waste and anerobic bacteria in your gravel. It will put out serious toxins than can kill fish when disturbed. Get an airpump and an airstone to aerate the water more. More oxygen will kill the anaerobic bacteria as beneficial bacteria takes over. If you have decorations in there, remove one and see if there is crud in the gravel under it or if gas bubbles rise from it. If so.....stop! Get your vacuum and suck out that gaseous mess before it kills more of the fish. If you have to, net the fish out for an hour or so to an aerated bucket of aquarium water and get the tank clean. Remove all the decorations and vacuum thoroughly. Changing the filters is actually a bad idea. It removes beneficial bacteria that removes ammonia and nitrite. Only rinse filter media. Rinsing will preserve most of the bacteria but gets rid of the crud that plugs things up. Thakns. Good Luck.

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