Snails keep dying but fish are fine...?

[FunInTheSun182]

I have a 10 gallon freshwater tank that started with 2 Mexican dwarf crayfish, 2 vampire shrimp, and 2 dwarf gouramis. Everything was great and everyone got along for weeks and weeks. My two vampire shrimp died a couple weeks ago, within 2 days of each other. They'd just gone through a molting, so I don't know exactly what the cause of death was. Ever since their death, I noticed how much waste was in the tank without them there to filter it. So I decided to get some snails. I moved the crayfish to a different tank so they wouldn't harass the snails, and they're doing fine.

I got a horned nerite snail, 2 Japanese trapdoor snails, and a mystery snail. I also got a clown pleco. The snails were okay the first few days, but then they became lethargic and didn't do anything. The nerite snail and both trapdoor snails have passed away. I moved the mystery snail to a Gladware container and she immediately started moving around; it's the most she's moved since I got her. I put her back in the tank to see what would happen; she became lethargic again. I put her back in the Gladware, she started moving immediately. I've also noticed the snails can't seem to grip onto the walls of the tank. When I put them against it, they can grab it, but they can't glide along it; it's like they get stuck and can't slide.

I tested the water parameters and everything was just fine, within normal limits. To be safe, I siphoned waste and did a 30% water change. The dwarf gouramis and the clown pleco are doing great, not acting sick or lethargic. So I just don't understand what's going on with the snails! I don't know if something could have happened to the water after the vampire shrimp passed, but I did the water change and scrubbed the walls, so I don't understand what's going on.

I also got some ramshorn snails for my other tank, and I put some of the min the gourami tank to see what would happen. They were fine for a few hours, then became lethargic and didn't move. As soon as I put them in a Gladware container, they started moving immediately and acted fine again.

Any advice would be greatly appreciated. I haven no idea what's going on, and I don't know how to go about fixing this. I thought the water change and cleaning would do it, but it seems to have not done anything. I'm at a loss!

 

[Fresh2o]

Death after molting can sometimes indicate low calcium, pH, and/or GH and KH.
The clown pleco might be adding too much to the bioload. How long has the tank been setup? Amount of water change per week? What have you tested and what results did you get?

 

[Autumnsky]

Has there ever been any medication in the tank? Copper and copper derivatives residue cause death of small invertebrates like snails.

Question of whether the filter has enough active BB, and if you are doing Fish In cycle you will need to use a test kit liquid tests are much more accurate.

My signature has a good article resource for learning about keeping a tank.

Also did you recently change the filter pad or clean it with tap water?

 

[TMaier]

Any heavy metals in the substrate? It killed all my snails and shrimp but the fish and plants were fine.