By Stacey Blood
Director Of Operations
Blue Shark Trading Company

So you just started your tank and your water is cloudy.  While there isn’t only one cause of cloudy water in aquaria, the typical cause at this stage is bacterial blooms.

These blooms are commonplace in aquaria and are characterized by a white, diffused blur throughout the water column.  Bacteria blooms can happen in later stages of aquarium keeping but are rare and typically the result of some major change in the ecosystem balance or nutrient levels.

The reason we see bacteria blooms most commonly in new aquaria is simply because it is usually the only time your tank has 100% new water in it.  Subsequently, your water changes will be in the 10-20% range, meaning up to 80% of your tank is your established aquarium water volume.

Main Factors

The two factors that allow a bacterial bloom to happen in new tanks are:

  • Gauss’ Law Of Competitive Exclusion
  • Nutrient load

When a full tank of water is introduced, it brings with it microbes that have survived the journey from your water utility or well as well as a treasure trove of nutrients on which to feed.  These microbes flourish, uncontested by other established biological activity, to win Gauss’ game of competitive exclusion.

Over time, however, these microbes begin to deplete the high, maximum nutrient load of a newly filled aquarium and begin to die off.  That is why water changes will only perpetuate your bloom.  Simply wait it out and the cloudiness will dissipate and reveal a crystal clear tank!


While bacterial blooms are an eye-sore, they at least come with a fringe benefit.  Upon clearing you will notice that your tank is crystal clear!  The life and death cycle of these blooms have a way of clearing up the water column to pristine ends! 

It’s rare to have bacterial blooms in the post set-up stage of you aquarium journey, but if it occurs you know what to do and that things will look extra clear afterward! 


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