Originally Posted by Homer16
How is it a bacteria bloom if there was no fish in it up until last night? Maybe I dont understand what a bacteria bloom is. My largest tank cleared really fast its just this one its driving me nuts lol. Will the fish be okay in this tank? Its cloudy but you can see into it and everything
This will not harm the fish, assuming it is a bacterial bloom. If it were sand particles, these might harm the gills according to some, but I think this would have to be particularly bad sand cloudiness.
Bacterial bloom refers to a multiplication of bacteria in the water column. Not to be confused with the "bacteria" we usually refer to in nitrification. There are many species of bacteria all having different functions (the good stuff) and of course there are harmful bacteria too (the disease bacteria).
A new tank frequently has a bacterial bloom (the initial cloudiness is almost always this) because tap water is usually loaded with microscopic-sized organics. When you add dechlorinator, it gets rid of the chlorine so bacteria can multiply, and with such a heavy food source, they are quick to do so. These bacteria can multiply in less than 20 minutes, each by binary division into two new bacterium, so you can see how quickly they can reach thousands.
This article I wrote on bacteria may provide some background, and there is a section on bacterial blooms: