Agressive danio

[mhorn327]

Hey all,
I have just set up my 20 gal yesterday and bought 2 white cloud minnows and 2 zebra danios to start cycling my tank. I was told these fish are very hearty and great for setting up the bacteria cycle.
My problem is that the one danio is bigger then the other three and is very bothersome. He constantly chases every fish that swims into open water and wont leave them alone till they hide against the glass at the top.
I am worried that this little jerk is going to stress out the other three and kill them eventually.

any recommendations would be great thanks!


-Mark

[Padams]

Zebras are a schooling fish and need at least 6+ to be "happy". You will see them flash all over the tank most of the time. They have been called "energizer bunnies of fish". Once you get numbers up it should calm down. The other reason might be you have 1M & 1F and ........ .

IMO add 4 more next week and keep going. A "booster" wouldn't hurt either.

[Lab_Rat]

Like padams said, danios are schooling fish and really need to be in groups of 6+. White clouds are also schooling fish that need to be in groups of 6+. They also prefer cooler, temperate waters which differ than many of the tropicals for sale.

Since you just set up this tank and it is not cycled, I would consider returning the fish and fishless cycling if you can. That would solve the problem of inappropriate numbers for two species of schooling fish and will give you time to plan out what fish you really want for your final stocking. Additionally, it will make cycling easier on you (less water changes needed since you're not worrying about keeping fish alive) and no fish will be stressed or killed in the process. If you're interested in more info on fishless cycling, there is a sticky about it in the cycling section.

If you cannot return the fish or wish to cycle using the fish in method (there is a sticky on that to read too), I would just wait it out and not buy any more fish until the cycle has completed. Or return the white clouds and use 2 other zebra danios to spread out some of the nippiness. I would also consider using Tetra's SafeStart to help cycle the tank (there is no good evidence that it is effective, but it's not going to hurt) or if you can possibly get some used filter media, that would be the best way to go. Good luck with whatever you do.

[MrJim]

Zebras are definitely chasers though it always seems more like sporting than aggressiveness.