Whats Wrong With My Mts?

[danele]

I've recently got 5 trumpet snails for my 28l tank which is home to one male betta.
At first all was well, buried in the sand through the day, lights off and they would be seen doing their thing.
2 weeks on and 2 trumpet snails are sat on top of the sand and have not moved for 3 days, and a third one has done the same for 2 days.
Taken one out tonight, and although its not coming out of its shell, there is movement
Whats going on?
I have sand, live plants and my ph is 7.4
Any ideas?

 

[phoenixgsd]

they are quite good indicators of poor water, when mine start comming out during the day its because i need a water change

 

[danele]

Now you've got me thinking, i changed 40% of the water 3 days ago, coincidently when it started