Cloudy water 2 days after set up


New Member
Apr 28, 2017
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Im very new to having fish, so just figuring things out. I set up my tank on Tuesday. I did everything as I should have eg rinsed the tank, rinsed the gravel etc I added the Bio-boost and Tap water conditioner as instructed to by the aquatic shop I bought the tank from and followed the directions on the bottles. Thursday morning I woke up and it had gone cloudy. I can see through it so it's not that bad. I was wondering if it could be a bacteria boom (I think that is what you call it)? I don't have fish in it at the moment but I do have a heater and filter. I haven't tested the water yet, but we are going to the shop tomorrow to talk to someone and get the kit to test the water. Any help would be appreciated on how to solve it. Thanks


Staff member
Global Moderator ⚒️
Nov 28, 2006
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Teesside, UK
It does sound like a bacterial bloom and these are very common in new tanks. However, the bacteria are not the ones we want to grow in the filter.

Bloom bacteria multiply rapidly and live in the water; we see them as the cloudiness. The good news is that once they have eaten all the available food they will die and the water will clear; the bad news is that it s impossible to say how long this will take as every tank is different.

Word of warning - when you have the water tested it will give perfect results and the shop will say it is OK to get fish. The reason that the water will be OK is because there are no fish in it and as soon as you put fish in it will become not OK very quickly.
Can i suggest you read this before getting any fish - but buy a test kit instead while you are at the shop. You will need one whether you do fishless or fish-in cycling.
The bottled bacteria products do not cycle a tank instantly; the best ones speed it up, the worst ones do nothing. It is always safer to use these products to hopefully speed up a fishless cycle rather than risk finding yourself doing a fish-in cycle.


Fish Fanatic
May 1, 2017
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The cloudy water is extremely common and should go away within 2 days. As for the instant cycle, essjay is right, the way instant cycles work is that they introduce bacteria to the water column but they usually also introduce ammonia neutralizer, this neutralizer is not considered a full cycle however, the way it works is that it changes the ion composition in the water that allow ions to attach themselves to ammonia, converting it to ammonium, thus making it harmless to fish. The problem with is is that your bacteria colonies are still undeveloped and will not be able to process ammonia long term. After about 48 hours the water chemistry will re stabilize and the ions will begin to separate again, turning the ammonium back into harmful ammonia. This is why it is not recommended to add fish until your cycle has had adequate time to establish, which can take weeks, although the instant cycle will accelerate this process, it does not create a fish-ready ecosystem.

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