Unhappy snails (apple & nerite)
 

My snails are not doing so well. They are very inactive and some of my apple snails have passed on. I have 5 nerite snails, 4 apple snails and 1 assassin snail. I also have a mussel, an african dwarf frog, and a betta which show no signs of stress.

The apple snails are laying around with their shells half-closed. When Ii pick them up they close their doors slowly. I sometimes find a nerite on its back not making any attempt to right itself. Some of the nerites are spending more time above the water line than usual.

Here is what I've already tried:

I thought the issue was PH related because the PH kept dropping to 6.4. I thought that a large stone in my tank, possibly gypsum, was affecting PH. So I replaced it with the more inert quartz for decorations. I also removed a moss ball that, when tested in a separate container, seemed to cause the PH to drop.

I was using Seachem's Neutral Buffer at the time. So I switched to using Prime to treat my tap water and brought the PH up over a few weeks via water changes. Now the PH matches the tap water and has been stable at 7.6 for a couple months.

The PH changes could explain why the original apple snails died. But the 4 current apple snails have only been in the tank for a week when PH has been stable. They were active the first few days, but have since declined.

I thought temp might be an issue as I read apple snails will live much longer at colder temperatures. So I moved the tank from 78F to 74F. Since they slowed down even more after that, I raised the temp up to 76F.

About a month ago I switched out the media in the canister filter to a more porous media. To avoid excessive cycling, I kept some of the old media in with the new media. This left no room for carbon, but I was advised that it's good to occasionally run the system without carbon.

I do regular water changes and clean out the canister filter about once a month. This tank has duckweed in it and the nice side effect is that Nitrates always test low. I also had the lfs test my water to make sure my kit hasn't expired. Current test results:

PH: 7.6
Ammonia: 0ppm
Nitrites: 0ppm
Nitrates: 5ppm

Tank is planted: banana plants, dwarf hair grass, red tiger lotus, anubis, corkscrew val, & echinodorus vesuvius. There were some other plants in the tank that I recently removed because of visual over crowding. Those lotus get big!

I have ordered a copper test kit just in case that is somehow an issue. I also removed the quartz crystals and a small buddha statue (in case they are leaching something) as of last night.

Any ideas on what else I can/should check?

Could it be that they are not happy having an assassin snail in with them?

I don't know but I have an Assassin snail in each of my tanks with my Apple snails and they pretty much ignore each other. The Assassin goes after the much smaller Ramshorns and the Apple snails have traveled right over the Assassin as though giving it a message. Not sure what the problem is here with these snails though.

OP I know that Apple snails go into a very inactive period that can last months from my understanding. Sort of like Hibernating. Could that be what you are seeing?

Actually, I just checked on the assassin and he's dead. He had been immobile for about 3 days.

That is what I assumed at first, but the behavior of the other snails suggests (to me) that something else is going on. Also, I could understand losing a couple apple snails during hibernation, but I've lost four so far.

I'm not sure if it was the moss ball itself, or if the moss ball was holding onto excess buffer. The PH issue was solved by removing the moss ball and lots of water changes without the buffer. PH has been stable a couple months, but my snails are still dying off.

I did order a Carbonate Hardness test as well, so I'll check that as soon as they arrive.

No shell erosion. The mussel seems to be fine. Mostly he just sits there, but occasionally he'll stick out his tongue/foot/whatever and maneuver into a better position.

Besides copper, are there any other heavy metals I can/should test for?

At this point only 2 of my 9 remaining snails are showing any signs of activity. Those two are nerites.

Is it possible that my lighting is too bright for them? I have 2-65W CF bulbs on a 15g tank.