Will rainbow sharks, guppies, and neon tetras get along in a tank?

The Tang, Clownfish, and Chromis are marine fish requiring a saltwater aquarium while guppies are freshwater fish. These fish are not compatible as they require two completely different setups to accommodate their different environmental needs. If you are going to set up a marine aquarium - a 20 gallon aquarium is too small for the fish you have listed. A small Percula Clownfish maybe suitable in a 20 gallon aquarium temporarily, but be prepared to upgrade to a larger aquarium as it grows larger. In general, 50+ gallon aquariums are recommended to properly house marine fish as they tend to grow large and require plenty of room to swim. If you are planning to set up a freshwater aquarium, a 20 gallon setup is adequate to house guppies.

I assume it is a male Beta? They typically are very aggressive and will kill other Fish. You could try to put a divider in the tank to keep them separate. I have seen those at most pet stores. Best of luck and thank you for using Pet Coach.

Betta are definitively very territorial and you may notice multiple fights for space at the beginning. Definitively the aquarium must have multiple spots for hiding like Terra Cotta Flowerpots and PVC Piping, moss or bushy plants, ornaments, rocks and driftwoods. This will avoid open fights and will provide good places to have some rest.

Bottom feeders such as plecos or corydoras catfish will do well in a tank of angelfish. Other community fish include silver dollars and the larger Tetra species. Monitor for fin nipping and remove fish if necessary. You have a lovely tank and the angels look very nice in it. Be cautious when adding fish as you may overload your tank. The angels will grow as will any additions and your tank may not be able to support the population. This could lead to poor water quality, aggression and sick fish.

Platys and guppies are usually both pretty docile, but sometimes it is the behavior of the individual Fish. Make sure there are plants for hiding and I would give it a try. Thank you for using Pet Coach.

Thanks for your questions about your tank. You have a number of fish in your tank already - a general rule of thumb is 2.5 square centimeters of fish per 3.8 liters. Depending on how large your fish are, you may be close to the carrying capacity of your tank, and you will also need to plan on how the fish in your tank will grow over time (mostly the rainbow sharks). If you are looking for tank mates for discus, it is best to look for fish that are housed in the same temperature zone, and occupy different areas in the water column than they do. Examples would be bottom feeders like cory catfish, those that live on the sides and bottom such as plecos, and those that are in the middle of the water column like some species of tetras. For the question about vacation - I would not recommend leaving your tank for that long without someone checking on it regularly. Power outages can be detrimental for tanks, and water changes or additions would likely be required. Also, automatic feeders also have the potential to fail, and this could cause a large spike in ammonia if a large amount of food was fed, and starvation if there was no food dispensed over a long period. I hope that helps to answer your questions, and thanks for using Petco Pet Education Center, formerly Petcoach.

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.