Hopefully a simple question

[imma24]

You say the tank has it's own built-in filter. Usually, one needs a filter rated at least twice the volume or gallonage of the tank. You might consider adding an extra (external) filter, and seed it with established media so it grows the BB colony faster.

The danio that is swimming erratically may have a swim bladder issue.

I agree with the filter issue. Many tanks come with a filter that is indequate for a stocked tank - therefore, a 10gal tank comes with one rated for up to 10gal which isn't enough for a 10gal with fish in it.

I also agree that the bacterial bloom would indicate you lost some of your BB along the way somehow.

I would also do larger than 25% water changes at this point (more like 50%) - even if they don't help the fish you mentioned, you want to avoid further stress/illness until you can start testing your own parameters.

[Allecto]

It would help us here in the U.S. to know what the equivalent of 125l is in gallons.

About 33 gallons.

[Goes to 11!]

It would help us here in the U.S. to know what the equivalent of 125l is in gallons..

No doubt .

It would certainly help if all of those in the US did know that but for whatever reason many apparently don't. It is something to strive for though.

It's not as if it is an extremely simple calculation or a search that Google literally completes for you. . . . Or is it?

[Honey Badger 1]

It would help us here in the U.S. to know what the equivalent of 125l is in gallons.

Do you ever post how many liters your tanks are for the many users here that don't live in the US? Don't you think it is a little rude to expect the rest of the world (the US is one of only three countries that don't use the metric system) to conform to your math inadequacies? For those of you who don't know how to convert liters to gallons the formula is very simple, (liters).264 or in this case 125 x .264 = 33. If this is still to much math to wrap your brain around there is a handy calculator that will do the conversion for you in the left hand menu.

Puber, skinny fish and swimming with its head down could indicate parasites. How long have you had the fish? If you have had them for a long time then I am probably wrong, but if not, it might be something to look into. PraziPro has always worked well for me.