Siamese fighter: Sick??

Question
I keep my beautiful siamese fighter in a community/breeding tank with swordtails and silver sailfin mollies.  I have noticed the past few weeks that he is getting a more and more bloated tummy.  I have already reduced the amount of food I feed my fish.  This morning I noticed some baby mollies and I placed them into a breeding net and when I came home lunch time I fished out the last remaining three and put them into the net aswell.  It was very weird for me that there where only 5 mollie babie's in total as mine normally have between 8 - 10 fry in one birthing.  Then I noticed with shock that my siamese fighter can barely swim because he's so big/fat!!  Could he have eaten the fry causing him to look so fat?  I did some research on the internet and he might also have constipation.  I feed him a varied diet but he does get his blood worms everyday...  (didn't know this could be harmful...)

OK now to all your questions:  
*100l tank:
*1 small pleco, 2 flying foxes, 2 horseface loaches, 2  
kuhli loaches, 1 catfish/pleco (not sure which it is but
its very peaceful),1 small pepper cory, 8 swordtails,
10 sailfin mollies and the siamese figher.  
*Don't know about the chemistry levels...
*I keep the tank at 27 degrees C
*I clean the tank twice a year but do monthly water
changes of about 50%. This is also when I vacuum the
gravel.

Answer
Hello Katja:  Your Siamese fighting fish may just have over eaten or he may have something called Dropsy... do a web search for this disease and look at the pictures... it is a very pronounced swelling of the fish usually caused by internal parasites or intestinal blockage... If your little guy is still eating I would try to feed him some live brine shrimp as they sometimes have a laxative effect.  If you feel as though this fish has dropsy you can
try to treat the fish but most fish eventually die... dropsy is one of those diseases where it is best to consider euthanization... If you decide that the fish must be put down... contact your local aquarium and ask them if they will do it for your or if they can tell you were to get the solution to do this.  Freezing fish to death is not very pleasant on the fish.... please keep me posted on your fish's progress... dave