Any snail from a pond or waterway that has birds using that waterbody, could be a host to parasites like worms. If you have snails in a separate tank for 6 months and keep fish and birds away from them, the snails with the parasites eventually die and you are left with disease free snails.
The snails act as an intermediate host for certain diseases and if you break the cycle by keeping snails away from fish, you stop the disease.
The most common diseases spread by aquatic snails are intestinal worms like tapeworm and thread/ round worm. You can use most dewormers in the aquarium and they shouldn't affect the snails because deworming medications are quite specific at what they affect, and they normally only kill worms.
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Most fish from pet shops also carry worms so I would buy fish, stock the tank, then treat everything for worms. Then your fish and snails will be clean. If you want anymore fish or snails after that, quarantine them and treat for worms while they are in quarantine.
You can use Praziquantel to treat tapeworm and gill flukes. And Levamisole to treat thread/ round worms.
Remove carbon from filters before treatment and increase aeration/ surface turbulence to maximise oxygen levels in the water.
You treat the fish once a week for 3-4 weeks. The first treatment will kill any worms in the fish. The second and third treatments kill any baby worms that hatch from eggs inside the fish's digestive tract.
You do a 75% water change and complete gravel clean 24-48 hours after treatment. Clean the filter 24 hours after treatment too.
Treat every fish tank in the house at the same time.
Do not use the 2 medications together. If you want to treat both medications in a short space of time, use Praziquantel on day one. Do a 75% water change and gravel clean the substrate on day 2 & 3. Treat the tank with Levamisole on day 4 and do a 75% water change and gravel clean on day 5, 6 & 7 and then start with Praziquantel again on day 8.
