for it.? What should i do for it? (its top fin has been bitten) and its slightly bleeding. Its in my hatchery BTW. Please hurry i dont want him to die. Thankyou.
You need to isolate the fish and treat with an anti-bacterial medication. Some medications are not invert safe so if it's still in the same tank with the crab it won't be able to be treated.
Rehome the crab - if it's a common species like rainbow or red clawed it's a brackish (not freshwater) semi-terrestrial (not fully aquatic) animal anyway.