My ID shark isnt eating.

Question
Thanks, my 90 gallon fish tank had been set up for about a month and a half. I have a 9 inch Iridescent shark and a 11 inch Red Belly Pacu.The pH level is about 7.5, temp is 78. I have not changed the water yet, but when I do I plan to empty about a little over 1/4 of the water. I had some big goldfish in the tank for the first 3 weeks. I bought the pacu and a week later I bought the ID shark. The pacu has been eating feeder fish and pellets fine. The problem is that my ID shark has not been eating anything (tiny guppies, feeder fish, or pellets). The pet store owner said these two fish would be fine together. I have had the shark for a little over a week now. Why is my shark not eating? what other food should I try with him? Should I try to return him?

Answer
Hi Sean;

The offered foods are just fine. He may just be lonely because Iridescents prefer others of their own kind to school with.  But they also grow to be over 2 feet long eventually so even one will be too large for your tank. I would return him to the store. Iridescents are also very nervous fish that bump into the sides and top of the tank when startled. They can easily break the lid off a tank as bigger or just get badly injured while still small. In my opinion they should not be sold for pets at all.

Check the water chemistry to be sure everything is okay. If ammonia or nitrite are elevated it could be affecting him and causing appetite loss. Make partial water changes (25%) as needed if ammonia or nitrite are up. Big fish make big waste and your tank's bio-system is still fairly new. It may need more time for it to balance out.

Your pacu needs some vegetables in his diet to thrive so feed him a salad every day day with his pellets. I fed my pacu peas, carrots, green beans, romaine lettuce, kernels of corn, broccoli, cut up grapes (whole ones can get stuck), bits of apple (peel on), pear, oranges, etc. Just rinse them and drop in the tank. It is healthier for your fish if you don't feed them live feeder goldfish, guppies, etc. I ran a pet store for many years and sold thousands of them over that time. They are shipped packed to the gills (literally) in plastic bags and stay there for hours where they can barely move before they reach their final destination. They are so incredibly stressed before they get to the fish stores that even those that look healthy can be diseased and spread those diseases to your healthy pets. There is also a low nutritional value in them from starvation after being transported for several days from farm to wholesaler to store. Just not a good deal for your fish.

Good luck...

At Your Service;
Chris Robbins