What's the best food for my Rosaline Sharks, Congo Tetras, and Pleco?

Thanks for reaching out. The most important thing you can do is maintain optimal water quality, and this means getting a test kit and testing frequently. Diet is important, and all fish have a dietary requirement for vitamin C. Vitamin C is not stable in fish food for more that a few months, so write the date of purchase on the can of food, and discard after 3 months. It is also recommended to alternate brands of food, as they are all slightly different. Since they have an exoskeleton, the only easy way to measure body score is around the belly. If concave, too thin. Determining illness is tough, so visualizing eating and activity, and comparing it to the past. Good luck.

Check the water chemistry and temperature. Use a home test kit or submit a water sample to test fro elevated ammonia or nitrite levels. Most pet stores will do this for free or for a small fee. Partial water changes can be done, if indicated, to stabilize chemistry and improve or maintain water quality. Ideally, you want 0 ppm ammonia and nitrites with nitrates at 20 ppm or less in a non-planted tank or 40 ppm or less in a planted tank. Use only aged or conditioned water that is temperature matched to prevent stress or shock. You'll need to keep the temp at the upper limits for Red Tails in order to keep the Angelfish comfortable. That would be in the 78F to 80 F range. Both have similar pH requirements, 6.8 to 7.5. You can fast the Angel for 2-3 days then feed bits of cooked, shelled green peas. This will usually resolve constipation and bloating. Pristine water quality may resolve the patch on your shark. Recommending a medication without more information or a clear image would be risky to the stability of the tank's nitrogen cycle. You can use plain aquarium salt (NOT table or Epsom salt) as a general tonic. It will reduce stress, improve gill function, may treat minor infection and aid in recovery. Dissolve 1 tablespoon per 5 gallons of water in a cup of tank water and gently pour it into the tank. Treat for 10-14 days then reassess the condition. A note on tank size: Although the two fish may be fine in a 15 gallon tank now, you will likely need a larger tank as they mature. Red Tails can reach 6-7 inches and Angels can reach 6-8 inches. At adult size, a 15 gallon tank will be insufficient and could lead to some aggression from either fish.

Add some protein to his diet. This can be in the form of live, frozen or freeze dried blood worms or blackworms. You can also use your preferred search engine to look for "earthworm sticks" to feed him. Check the water quality as well (hardness, pH, etc.). Make adjustments as needed. Low water temps may cause stress and illness. Check your tank heater and temperature.

Rainbow sharks are generally aggressive with other fish and are not a good match with peaceful fish. Tetras and guppies are generally fine to live together. When picking out fish, you want to keep a community that all have the same aggression levels. The store clerk will be able to help you with that information. I hope this is helpful and please feel free to post any additional questions.

Check the water temperature. This species does best between 68 F and 77 F. Low temps can affect appetite in fish. He may be near the heater for warmth. Check the water chemistry as well. Use a home test kit or submit a water sample for testing. Most pet stores will do this for free or for a small fee. Aim for 0 ppm ammonia and nitrites with a nitrate level of 20 ppm or less. Partial water changes can be done to stabilize chemistry if indicated. Use only aged or conditioned water that is temperature matched to prevent further stress or shock. If it is a "new" tank, there may not be enough food/algae on the bottom for it. Use sinking pellets or toss in some vegetables or greens. Be sure to remove any uneaten food after 24 hours to prevent it from fouling the water.

He may have internal parasites. maintain pristine water quality and confirm stable water chemistry. This can be done by using a home test kit or by submitting a water sample for testing. The local Petco may do this for free or for a small fee. Perform a partial water change, no more than 30% total volume at a time, if indicated. use only conditioned water that is temperature matched to prevent further stress or shock. Check the water temperature as well, since low temps can affect activity, appetite and digestion in fish. Anywhere between 72 F and 80 F is acceptable. Keeping it at the higher end may aid in digestion and defecation. Consider a broad spectrum parasite medication. You can find one in the Aquarium section at the local Petco. Follow label directions carefully and remove the carbon filter insert during treatment if indicated.

Glass catfish should be kept in groups of 5 or more or they will not feed properly. They will eat flakes better when there is competition from other glass catfish. Glass catfish do prefer other foods and need more than flakes. Try to get brine shrimp, blood worms, or California blackworms from your pet store. It is also important to keep them in a dusky environment, they do not like bright lights, and will be more active in the evening and night, and therefore also eat during that time. Water temperature should be around 75–81 °F, better at the high end.