Bacterial Bloom/New tank Syndrome

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Hi all,

Just the overall consensus online on the topic is to let the colonies get settled before doing a water change.

I had heard that doing water changes in a new tank is actually the #1 thing you don’t want to do during a new tank bloom. With no root system, no pre-introduced bacteria, and new water doing a water change doesn’t allow the bacteria to get a hold where they need to and can make the bloom last longer than it needs to.

Honestly listen to what


tells you. Don’t listen to who ever is telling you not to change water. If they also tell you to add ammonia to cycle your tank? don’t listen to that either.

Scientists now know huge amount more about the microbial processes that go on aquariums, it is just that very little of that scientific knowledge has trickled down to most forums. The past <“

truly is a different country

“>, but forums and LFS advice hasn’t always caught up.

Have a look at page 4. of <“

Bedside Aquarium


Water changes

The micro-organisms that you have in the tank aren’t the same as the ones that are responsible for nitrification. They are opportunistic “heterotrophic” bacteria and fungi that have bloomed due to the availability of easily digestible sugars and nitrogenous compounds (from the wood and substrate). You just need to keep syphoning the obvious bloom out when you change some water.

Water changes will dilute the these compounds and as they go your bacterial bloom will decline. If you don’t change any water you run the risk of low oxygenation levels occurring as the bloom declines, and those nutrients being continually re-cycled within the tank.


The traditional view is that nitrification is carried out by a limited range of bacteria and that there is a temporal sequence where the level of ammonia (NH3/NH4+) oxidising bacteria has to build up and only after that will the bacteria the oxidise nitrite (NO2-) to nitrate (NO3-) occur, and that you need high levels of ammonia and carbonate hardness for this process not to stall, but none of that is true in aquariums.

cheers Darrel

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