Molly wont swim

Question
We have had this molly in our tank for a little over two months.  It's been very active and fine until two days ago when it began sitting on the rocks at the bottom of the tank, not moving a whole lot.  My son noticed that it seems very bloated.  When we feed the fish it tried to swim to the top the first day or so to eat but quickly sank back to the bottom.  It tries to eat food off the bottom.  We have a 10-gallon tank with three tetras, two mollies, a bottom eating fish and a snail.  The only new addition to the tank is the snail which we bought last week.  we change the water monthly and filter biweekly and we do condition the new water.  The tank water looks fine and all the other fish seem fine.  I don't know what to do.  

Answer
Hi Tessa;

It sounds like it might be constipation that is affecting it's swim bladder. The swim bladder is a hollow organ inside the body below the spine that controls buoyancy. When the fish wants to go up in the water it inflates with blood gasses. When the fish wants to sink down in the water, the blood gasses dissipate. A failed swim bladder will be unable to "inflate" so the fish can't float. A fish that loses the use of it's swim bladder does not usually regain it again I'm afraid. Many fish do live normal lives otherwise though. They learn to compensate and do quite well.

Sometimes constipation puts pressure on the swim bladder and the fish is helped by getting the bowels moving properly again. Try feeding the fish cooked green peas popped put of their little round shells and broken into little bits. Peas have a laxative effect. Feed no other foods until the fish has normal bowel movements again. Mollies need greens in their diet like cucumber, romaine lettuce, spirulina algae, algae tablets, algae flakes and live aquarium plants. All the other fish will like these foods too and it's good for them. They may not know what it is at first, but they will get the hang of it in a couple of days. ;-)

Water changes really should be made more frequently than once a month. Especially for livebearing fish such as mollies since they require very clean water. Replace 25% to 50% of the water weekly so the water quality is more consistent. It used to be common practice to add salt to tanks with mollies, and they can even be acclimated to live in salt water, but they really don't need it. Clean water works much better than anything else in keeping all the fish healthy.

Here is more info about mollies and their needs;

http://badmanstropicalfish.com/profiles/profile24.html
http://www.thetropicaltank.co.uk/Fishindx/molly1.htm
http://fish.mongabay.com/species/Poecilia_sphenops.html
http://species.fishindex.com/species_3214poecilia_latipinna_molly.html

I hope your molly feels better soon.....

At Your Service;
Chris Robbins