hey damo! Welcome to AA. I hope we can figure out what's going on with your fish! Some of the things that will help us better are to know what your water parameters test as (ammonia, nitrite, nitrAte, pH). To me it looks a little like fungus, but I really can't tell by the pictures. The first thing I would do is to make sure your water quality is good. This is the basis for good fish health! I'm glad to hear you are upgading your tank, as it is heavily stocked with just the mollies alone! They will appreciate the bigger tank size
The heavy bio-load in this tank (too much poop, too little water
) is probably a big contributor to why you are seeing disease pop up in the tank.
The other thing I would mention is unfortunately Pamiam is right about bala sharks and red tails. (though I disagree about mollies, they benefit from a little salt, but don't need brackish water)
The pet store duped you
Bala sharks need a
minimum of 200 gallons (757 liters), grow to be over a foot (35 cm), need to be kept in groups of the same species, and are very active. IMO pet shops should not even allow them as they are not suitable for the aquarium.
Learn more about balas here.
Red Tails average 6 inches (15cm), will mostly chase fish away from their territory and then retreat; therefore, it is important to ensure the aquarium is large enough to allow the redtail some space to call its territory. When two red tails cohabitate, they have been known to become extremely territorial with one another. One shark will become dominant and will continually chase and harass the submissive shark, preventing it from feeding and resting. This will often result in the death of the submissive redtail shark. Aquariums should be at least 45 gallons (170 litres) or larger for a comfortable community. Redtails are bottom dwellers, so it is strongly suggested that one does not introduce them into an aquarium with another bottom dweller, as they will constantly pester and harass it. They also should not be introduced to communities containing other shark-like fish.
I would take them (the sharks) back if your not considering getting a HUGE tank.
Again, water quality issues are probably the underlying cause of your fishes looking sick, because of the huge bio-load (lets admit too, mollies are eating and pooping machines!
). Try doing a water change (50%), get your water tested, post your results and hopefully we can help you lots! Good luck, I love black mollies
EDIT: if you don't have a test kit, most fish stores will test it for free, just make sure to write down the results so you don't forget!
