It sounds like these are brand new tanks… I would begin by chalking this up to a great experience to learn why it’s best to do thorough research / education before buying a pet. I don’t mean that to be rude in any way, but yet mean it quite literally.
Cycling the tanks is very important. The ammonia that the fish produce is toxic and any build up will have long term effects on the fish. Even if it doesn’t kill the fish the fish will suffer long term effects from it (shortened life span, less vitality, less coloration… all in all a drab/gloomy fish).
Has your other tank been cycled to prepare for the Blue Dempseys? Blue Dempseys are delicate fish when young and if the stress they experience from dealing with ammonia/nitrite will likely kill them or open them up to a parasitic infection that will kill them.
Heavy water changes is the best way to reduce ammonia/nitrite… I have no personal experience with them but you may want to try one of the “instant cycle” chemicals on the market. I’ve heard mixed reviews on them…
Lastly, as mentioned, your 20 gal is way overstocked even with these couple of fish. Oscars grow very fast and are quick to develop Hole in the Head disease in poor water conditions. Red Devils are very aggressive and are likely to kill tank mates when crowded.
If your other 20 gal is properly cycled, it will make a decent home for two baby Blue Dempseys for a while… but will definitely need to be upgraded eventually.
Best of luck…
Cycling the tanks is very important. The ammonia that the fish produce is toxic and any build up will have long term effects on the fish. Even if it doesn’t kill the fish the fish will suffer long term effects from it (shortened life span, less vitality, less coloration… all in all a drab/gloomy fish).
Has your other tank been cycled to prepare for the Blue Dempseys? Blue Dempseys are delicate fish when young and if the stress they experience from dealing with ammonia/nitrite will likely kill them or open them up to a parasitic infection that will kill them.
Heavy water changes is the best way to reduce ammonia/nitrite… I have no personal experience with them but you may want to try one of the “instant cycle” chemicals on the market. I’ve heard mixed reviews on them…
Lastly, as mentioned, your 20 gal is way overstocked even with these couple of fish. Oscars grow very fast and are quick to develop Hole in the Head disease in poor water conditions. Red Devils are very aggressive and are likely to kill tank mates when crowded.
If your other 20 gal is properly cycled, it will make a decent home for two baby Blue Dempseys for a while… but will definitely need to be upgraded eventually.
Best of luck…
