Trumpet snails trying to escape

[waldo]

I did a 50% water change today then added a bit of melafix since I've had some bacterial issues in the tank lately. Now some of my Malaysian trumpets are making for the water surface. I'm assuming this is from the melafix, do you think the snails will survive? I have quite a lot of them and only the largest snails seem bothered.
Keeping the fish healthy is my main concern and I can always replace the snails but I'd rather not have a large die off to foul the water.

[madagascariensis]

you have diagnosed correctly that something is bothering the snails, causing them to surface, however I don't think it is the melafix that is directly causing this.
snails surface when the water is bad or there is low oxygen. since you just did a water change, I don't think you have dirty water but maybe there was something in the tap water that was bothering them, or they are getting used to
the new parameters of the tap water(tank water slowly deviates from tap water until the next water change). slightly more far fetched: melafix is organic, so while it kills some bacteria, it can be food for other bacteria. in the case that your tank has a particular species of bacteria that can utilize melafix, they may be multiplying and depleting the oxygen content of your water.

[waldo]

The snails reacted within 30 min of adding the melafix and the water was conditioned before adding it but anything is possible. My filter has a oxygenator built in, I'll turn it on for a bit and see if it helps.
They don't seem to be reacting quite as bad, I only see a couple high up on the walls now. I generally only do a 25% water change, guess this one was a bit more then they liked.