Cloudy water


New Member
Dec 9, 2019
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Hi! Newbie here! My son wanted fish for Christmas and I’ve read up and understand that the tank needs to be set up in advance. I cleaned all the stones and ornaments 3x (the water looked clear), soaked the bubbler, put water in and the aqua safe and away we went!

The water was perfectly clear until day 5 but now has gone cloudy! There are no fish in there yet. Do I do a water change or let it run for a couple of days to see if it sorts itself out? Tia x


Staff member
Global Moderator
Nov 28, 2006
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Teesside, UK
Cloudy water is very common in new tanks. it's called a bacterial bloom, but the bacteria that cause it are not the ones we need to grow. The bloom bacteria live on organic matter, and new tanks are full of organic mater - from the water you filled the tank with to plasticiser in all the new plastic stuff. Water changes don't get rid of it because the bloom bacteria multiply very quickly so as soon as the new water goes in, the few bacteria left start multiplying and the cloudiness is back very quickly. The good news is that once they've eaten all their food they die off and the water clears. But it is impossible to say how long this will take as every tank is different.

Have you read up on cycling a tank? Before fish go in the tank, you need to have grown two colonies of bacteria. There are bacteria products, of which Tetra Safe Start is the best, but the best way to use it is to speed up a fishless cycle
Leaving a tank to just run without adding anything won't get it ready for fish.