Is it safe to add another Oscar fish to my existing tank?

Thanks for reaching out. Oscars are fairly aggressive and will try to eat each other, depending on their size. Be prepared to separate if needed and monitor interactions. Keep them well fed and provide plenty of hiding locations. Good luck.

A 55 gallon tank is truly not large enough for an Oscar. Usually they are housed singly or in a mated pair. A single adult Oscar should have around a 75 gallon tank MINIMUM and a pair needs 100G or larger. Here's a bit more info on Oscars https://www.petcoach.co/article/oscar/

As long as thee oscars are small there will be no problem, however they grow very fast and they will eat all your other fish except the gouramis. So yes, you will need a separate tank for them and preferably at least a 40 gallon tank. The same is true for the parrots, another cichlid species.

I would strongly recommend against keeping these 4 fish in one tank. Oscars can reach 12 inches when fully grown. JDs can reach 8-10 inches. You will run out of tank space eventually, or fish if they, being cichlids, become aggressive.

That would depend on the size of your tank and the size of the oscars. Arowanas need a lot of space usually. I have seen them successfully being kept with arowanas before, but the oscars must be at least the same size of their mouth, not smaller. Unfortunately there are not fixed ruled and the only way would be to try them out together. Hope this answer was helpful, but please do not hesitate to contact us again on the forum or by requesting a consultation if you have any more questions or to discuss it any further.

All these fish can grow quite large. The loach would be the "smallest" at about 6 to 8 inches when full grown. The Oscars can reach lengths of 18 inches and the Texas cichlid and sharks can reach a foot in length. All these fish will require much larger tanks than the ones you have now. The three Oscars alone would do best in a 125 gallon aquarium MINIMUM. The others may thrive in 55 to 75 gallon tanks. To leave them in small tanks will cause stress, aggression and likely infection.

If you put an Oscar in with your Tetras, they will be harassed and eventually eaten. Use a home test kit or submit a water sample for testing to check chemistry. Aim for 0 ppm ammonia and nitrites with a nitrate level of 20ppm or less. It can be slightly higher if you have live plants. If there is still ammonia present, the tank is still cycling. The cloudiness may be micro-bubbles which will eventually resolve or it could be a bacterial bloom which will also resolve once the tank has cycled.