Hi trouble with betta

Question
hi, recently i had bought a aust. blue lobster and he had pinched my betta fish's back lower tail and the lower back part of his body. he has a cut on both sides hes been alive for a day now but hes not acting himself. he is usually VERY active and now he is just sitting on top of my heater he still swims a little bit but when he does it seems like hes a rock and sinks to the bottom. i was wondering what i could do for him, he is my girlfriends and she likes him alot. just today i got rid of the bastard crayfish. but please if there is any advice you could give me you would be a lifesaver..literally. thank you!

Answer
I am sorry to hear you had a bad experience with the crayfish, the pet store should have informed you that it is aggressive and should never be with fish like bettas. Assuming the betta does not have any signs of a disease from the stress, white spots, fuzzy white growths, or other signs not associated with the injuries, there are some things that might help. Go to your local fish store and get a product called, Stress Coat. Fish have a natural thin coating on their bodies, almost like an oil, that helps them heal and protects them from diseases and parasites. When a fish gets injured or stressed, the coat tends to diminish some and the fish is more suseptable to problems like sickness or death. I would advice getting that product and following the directions for the dosing. However, do not put more than the recommended dose in the water, as this can cloud the water in just a few hours. If the water clouds, just do a partial water change, making sure to replace with water of the same temp, every day until the water clear some and then it should continue to clear itself with time. This treatment should help to cover the injuries with the natural coating the fish produces quicker than the fish can do itself. Other than this, there is really not much you can do. Just make sure the fish eats, if it doesn't, try some variety like frozen brine shrimp or another different food, but do not overfeed. If you try the different foods and the fish still does not eat, get a very small feeder, the smallest you can find. This should give the fish some nutrients even when it wont eat and this should help the fish heal. Finally, just make sure there are no other fish in the tank who might pick on the betta and make sure the water is the right temp and try not to stress the fish out in any way. With any luck, the fish could heal and survive. I had a baby angelfish many years ago when I first started keeping fish. I had bought it with two siblings. Well, as they began to grow, the siblings began to pick on one of them and soon they had eaten the weakers entire fins. The angelfish had no fins and looked pretty much done with. I removed the aggressive angels and made sure the injured fish was not stressed in any way and no other fish could injure it. I did not think it would survive. Soon, the fins began to grow back! I was so excited. The fish completely recovered with even more amazing fins than before. I had that angelfish, through near death to full grow, for over 7 years. So, while your betta may not make it, dont give up. Just try to baby it. I hope it survives. Please let me know if you need more help or clarity in any of my instructions. It may take time, so as long as the fish it still alive and not getting diseases or parasites, keep trying to help it recover. Let me know if you need more help.