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Bacterial Blooms Explained


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#1 backtotropical

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Posted 18 June 2008 - 12:57 AM

Bacterial Blooms - Explained

Every fishkeeper has experienced a bacterial bloom at some point. They are common in new set-ups which are cycling, but can happen at any time. The water goes cloudy, almost like someone has poured a drop of milk into the tank, and no matter how many water changes you do, it doesn't go away. Sound familiar?

I hope to explain here exactly what a bacterial bloom is, the effect it can have, how to treat it and how to prevent it.


The Nitrogen Cycle

To fully understand about bacterial blooms, a knowledge of the Nitrogen Cycle is required. If you are unsure of the Nitrogen Cycle or don't know what it is, it may be helpful to read the linked topic below first. This is particularly relevant if you have recently set up the tank, as the cloudiness is most likely an indication of other problems.

The Nitrogen Cycle


What is a Bacterial Bloom?

There are 2 types of bacteria at work in our tanks:-

Autotrophic Bacteria - Bacteria capable of synthesizing its own food from inorganic substances, using light or chemical energy. Our beneficial filter bacteria are autotrophs.

Heterotrophic Bacteria - Bacteria that cannot synthesize its own food and is dependent on complex organic substances for nutrition. The heterotrophs in our aquariums mineralise the organic waste (break down the uneaten food, fish waste, dead plant matter etc into ammonia).

Contrary to popular belief, it is commonly the heterotrophs which are seen in our bacterial blooms, not our trusted autotroph nitrifiers.

It is the heterotrophs which are primarily responsible for creating the "bio-film" (slimy residue found on the tank walls and ornaments) which builds up in our aquariums.

The heterotrophs are generally bigger than the autotrophs and therefore don't attach themselves to surfaces with the same ease. They also reproduce much more quickly. Heterotrophs can reproduce in around 15 - 20 minutes, whereas autotrophs can take up to 24 hours to reproduce.

In a newly set-up aquarium, the heterotrophs get to work quicker than the autotrophs, causing the 'cycling bloom' we so often see. Blooms are almost certainly heterotrophic if they are caused by a build up of organic waste in the substrate, which most, if not all, are.

Bacterial blooms are common in tanks with apparently no organics present (for example, where all that is in the tank is water and ammonia for a fishless cycle). This is caused by the dechlorination of the water suddenly enabling the water to support bacterial populations. The heterotrophs immediately get to work on the organics in the water itself. The severity of the bloom and even whether a bloom happens at all is dependant upon the level of organics contained in the water supply.

Our autotroph nitrifiers are strictly aerobic (require oxygen), but the heterotrophs can be facultative anaerobic (they can switch between aerobic and anaerobic function depending on their environment). Therefore the heterotrophs in the substrate will be in their anaerobic state and breaking down the organic waste into ammonia, but if they bloom up into the water column, they will switch to their aerobic form and will start to convert the ammonia back to nitrite, although very inefficiently. The heterotrophs are around 1,000,000 times less efficient at ammonia oxidisation than our beneficial autotrophs as the heterotrophs are not true nitrifiers.


The Effects of a Bacterial Bloom

Most of the bacteria in the aquarium are aerobic as it is a oxygen dominated environment, and these bacteria require lots of oxygen. When the heterotrophic bacteria bloom into the water column and switch to their aerobic state, this is a big drain on the oxygen content of the water. Oxygen depravation is the only risk to the fish which i am aware of during a bacterial bloom, as the heterotrophs themselves are harmless to fish, so good advice is to increase aeration! :good:

To help you to understand why bacterial blooms occur, overfeeding ,dead fish or dead plant matter will cause a rise in the reproduction of the heterotrophs in order to break down the organic waste, they re-produce too quickly to be able to attach themselves to a surface and this causes a bacterial bloom. As the ammonia production increases due to the increased mineralisation, the nitrifiers are slow to catch up (as i said above) and so you see an ammonia spike until the autotrophs reproduce enough to take care of it. Contrary to popular belief, bacterial blooms cause an ammonia spike, not the other way around.

It is unclear whether the autotrophic nitrifiers ever bloom into the water column or if they simply multiply too slowly to cause this effect.


Treatment and Prevention of Bacterial Blooms

A thorough gravel vac will certainly help the situation, as will trying not to overfeed. Also, increase aeration as I noted above. Water changes will probably not clear the cloudiness as when you remove the free-floating heterotrophic bacteria, the others will reproduce more to compensate. Given the reproduction rate of the heterotrophs, it would require a 50% water change every 15 - 20 minutes just to stop the bloom getting worse, and even more if you want to make any progress towards clearing the bloom.

However, water changes won't exacerbate the situation as it will be heterotrophs (which are producing ammonia) which are removed from the water column via the water change. A water change will remove virtually no nitrifying autotrophic bacteria from the tank at all as 99% of the nitrifiers are housed in the filter, not in the water column. Water changes are not essential in clearing bacterial blooms, as left alone, they will usually dissipate within a matter of days.

Reducing the amount of organic waste in your tank is the ultimate solution to treating a bacterial bloom, and avoiding a build up of organic waste in the tank is the best way to prevent a bloom. The best way to do this is to maintain a regular aquarium husbandry routine involving water changes and substrate vaccuuming.

As I said above, blooms are common in tanks with apparently no organic waste present, most commonly when only water and ammonia are in the tank for a fishless cycle. In this case, there are few easy ways to remove the organics from the water, and so my best suggestion is to sit it out and wait. Water changes with purified water would help as it would dilute the concentration of organics in the water. Reverse Osmosis water would be ideal in this situation, however i would suggest that patience is the cheaper and more environmentally friendly option.

A bloom in an established tank indicates that there is a problem which has allowed a build-up of organic waste, usually in the substrate. This can be caused by excess dead plant matter, over-feeding which leaves food lying around the tank, or leaving dead fish in the tank. None of these are desirable in an aquarium and a bloom in your established tank will certainly indicate one or more of these causes present in the tank. If you experience a bloom in an established tank, improve your husbandry.

Please note: Unless otherwise stated, all text and images in this post are copyright Backtotropical, 2008-2012.

#2 Miss Wiggle

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Posted 18 June 2008 - 07:12 AM

really good BTT, I would just add a little bit at the end explaining that a bacteria bloom in a cycled tank can be a sign that something is wrong with your routine, be it overfeeding or not enough cleaning or even an underperforming filter, so if you get a bacteria bloom while often a good gravel vac will get rid of it, you should look to prevention as well and try to work out what's gone wrong to cause it. :good:

#3 kewskills

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Posted 18 June 2008 - 08:05 AM

Very good piece of work :good:

#4 rabbut

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Posted 18 June 2008 - 11:29 AM

Very informative reading :nod: As Miss Wiggle surgests, mebe adding a little on prevention could be useful. With that type of information I'd judge it pinworthy :good: It's quite interesting to see that the ammonia spike associsated with bacterial blooms is acctually the result of the bloom itself. Any chance you could include a source or two, as some may be sceptical of that inforemation :nod:

All the best
Rabbut

#5 backtotropical

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Posted 20 June 2008 - 10:14 PM

Thanks for the replies and your points are noted. I'll do some more work on it later tonight. :good:

BTT

#6 backtotropical

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Posted 30 October 2008 - 08:44 PM

Now updated.

Any further comments?

I'd really like to get this pinned as it seems to be a frequent topic in 'New to the Hobby'. A pinned topic would serve the boards well IMO.

Cheers :good:

BTT

#7 Miss Wiggle

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Posted 30 October 2008 - 09:18 PM

Now updated.

Any further comments?

I'd really like to get this pinned as it seems to be a frequent topic in 'New to the Hobby'. A pinned topic would serve the boards well IMO.

Cheers :good:

BTT


i agree, have you dropped rdd a pm about it? as he's the most frequently active mod in the new to the hobby section if he agrees i'm sure he'll champion it in the mods forum. :good:

#8 backtotropical

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Posted 30 October 2008 - 09:21 PM

Thanks for the support MW. Much obliged! :good:

I will PM RDD now.

Edited by backtotropical, 30 October 2008 - 09:21 PM.


#9 quantumnerd

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Posted 30 October 2008 - 10:10 PM

Would a UV sterilizer do the trick?


After all, UV light kills bacteria, and bacteria are responsible for these blooms, right?

#10 Nick16

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Posted 30 October 2008 - 10:16 PM

1 request for this being pinned

#11 drobbyb

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Posted 31 October 2008 - 02:50 AM

1 request for this being pinned


I second that motion.

#12 waterdrop

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Posted 31 October 2008 - 11:15 AM

BTT, I would probably say that the biofilms are "primarily" the result of the heterotrophs. The biofilms are probably the result of a mix of a number of species that span the whole range of both the heterotrophs and on into the chemolithic autotrophs. I've been looking through some of the literature to find you a ref but to no avail - there's some work done for nasa on long-range waste processors that gets close to the topic but in general its hard to find good refs. I do believe in both cases, the heteros and the autos, the ones we care about are just the eventual winners out of a small group of species that can be present, but the several species types are still there, just in smaller numbers than the winners. Make sense?

Regardless of that kind of detailed stuff, articles like this should be clear, straighforward and useful and this one is. I'm definately another who thinks it should be pinned.

~~waterdrop~~

#13 Miss Wiggle

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Posted 31 October 2008 - 11:23 AM

Thinking about target audience here, the vast majority of bacteria blooms that we see are in new tanks, the topic assumes a reasonable knowledge of the cycling process which beginners often don't have. So perhaps a caveat at the top saying you need to understand the cycling process first, if you don't then here's a link.....

If someone's just got a new tank, put some fish in and the waters gone cloudy 2 days later chances are they'll be asking about that rather than about cycling, yes we usually pick up if it's a cycling tank and get the info to them that way but because the two are so often linked i think it would be worthwhile practically linking the topics.

#14 waterdrop

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Posted 31 October 2008 - 11:31 AM

Yes, that makes sense MW, good thought.

You made me think we need "fishipedia" :lol: ... you know how every few words in wikipedia are blue links? So much of our beginner stuff is all a tied together circle.

~~waterdrop~~

#15 jonnyf84

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Posted 31 October 2008 - 11:46 AM

very good btt, i see this topic around regularly so it should be a big help to people, as MW said, provide a link to the pinned cycling threads and it will be the complete thread.

I was very pleased to see someone highlighting the point that a simple water change will not solve the problems of a bacterial bloom.

good work.

#16 backtotropical

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Posted 01 November 2008 - 06:35 PM

BTT, I would probably say that the biofilms are "primarily" the result of the heterotrophs. The biofilms are probably the result of a mix of a number of species that span the whole range of both the heterotrophs and on into the chemolithic autotrophs.


Absolutly correct WD. thanks for pointing out my oversight. Now amended. :good:

#17 backtotropical

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Posted 01 November 2008 - 07:39 PM

Thinking about target audience here, the vast majority of bacteria blooms that we see are in new tanks, the topic assumes a reasonable knowledge of the cycling process which beginners often don't have. So perhaps a caveat at the top saying you need to understand the cycling process first, if you don't then here's a link.....

If someone's just got a new tank, put some fish in and the waters gone cloudy 2 days later chances are they'll be asking about that rather than about cycling, yes we usually pick up if it's a cycling tank and get the info to them that way but because the two are so often linked i think it would be worthwhile practically linking the topics.


Good comment MW. I totally agree. I have amended the article to include a link. :good:

#18 Miss Wiggle

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Posted 02 November 2008 - 10:16 PM

good stuff :good:

#19 rabbut

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Posted 02 November 2008 - 11:12 PM

Any chance you could put an underlined title over the prevention section? Just makes things easier to find and quote later ;) After that, good for a pin IMO :good:

All the best
Rabbut

#20 backtotropical

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Posted 03 November 2008 - 08:00 PM

Any chance you could put an underlined title over the prevention section? Just makes things easier to find and quote later ;) After that, good for a pin IMO :good:

All the best
Rabbut


I have now split up the article into easily manageable sections to make it as user-friendly as possible.

Cheers :good:

BTT




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