Can 5 skunk cories and 4 guppies live together in a 20-gallon 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.

In general these fish can all be housed together safely. The one thing to keep in mind is the amount of space needed per fish to maintain a safe and healthy environment. Each 1in of fish needs 1 gallon of water. So in a 20 gallon tan you can have 20 inches of fish. The Pleco is the only one I have concerns with as some varieties can grow quite large. Check with your local pet shop as to what needs best suit this type of fish or what type of fish suit your tank best.

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.

You should use one or two small, inexpensive but hardy fish to cycle a tank. Ideally, the tank should be cycled empty to prevent fish losses. You can also use a quick start product to speed up the cycling.

Thanks for reaching out. The general rule of thumb with good filtration is to have 1 " fish per 12 liters (3 gallons) of water. So starting with 10-15 should be good, but remember babies increase the bioload significantly, so continue to monitor water quality and allow your biological filter time to respond. Good luck.

Check the water chemistry and water temperature. If it is a new tank, it may not be properly cycled and could be undergoing and ammonia or nitrite spike. Either can drive fish to the surface or to one area of the tank. Submit a water sample for testing or use a liquid master test kit at home. Aim for 0 ppm ammonia and nitrites with nitrates at 40 ppm or less. Water temp should be in the mid 70s F. Perform a partial water change (30%) if necessary to stabilize chemistry and maintain water quality. Use only aged or conditioned water that is temperature matched o prevent stress or shock. Survey the area around the tank to rule out negative stimuli such as bright/direct light or loud noises/vibrations. These can also stress fish and cause them to move as far away as possible. Make sure the tank is large enough to support 8 guppies. Overcrowding can cause stress and aggression. Lastly, provide plenty of cover in the form of live or artificial plants. Guppies prefer cover and guppy fry (babies) need it or they will get eaten.

Adding more fish would likely cause overcrowding. This, in turn, could lead to stress, illness and aggression. You are probably at or very close to maximum capacity, especially if you have fish that are still growing.