Why Do Algae Blooms Occur In The Home Aquarium

Algae blooms can occur at any point in a home aquariums life but normally algae blooms occur during the start of the aquariums life.

When the home aquarium is first started everything is new. All the equipment, the sand, the rocks, the water etc are new. The aquarium needs time to settle in.

A good example of this is the sand. Quite often near the start the sand can become covered in what looks like a dusty brown covering. Quite often this is due to the silicates in the sand. When the silicates are all used up the algae simple disappears – quite often overnight.

As already said though an algae bloom can happen at any time especially if the water quality is not maintained at optimum quality. A couple of nutrients which can cause problematic algae to occur is nitrate and phosphate. The trouble in this instance is that the algae is using up the nitrate and the phosphate in the water therefore when the aquarists checks the parameters they show quite low, however behind the scenes there is a potential problem.

Another area is not looking after the equipment correctly. Two areas which spring to mind are the protein skimmer and the aquarium lighting.

If the protein skimmer is not maintained correctly then not all of the dissolved organic substances etc will be removed from the water and will be processed by the aquarium filtration and will therefore create nitrate etc which otherwise you would not have had.

If the light bulbs are not changed in accordance with manufacturers recommendations then the lighting will be below ‘par’ and could be producing lighting which is at the wrong end of the spectrum and algae which likes this type of colour could start to thrive.

There is another aspect which springs to mind and that is water flow. If there is not enough water flow in the aquarium or even in areas of the aquarium then algae can start to grow in these areas, cover the rocks perhaps even the corals.

The trick is to ensure that you maintain the aquarium correctly – perform all the required care and maintenance and attempt to keep the water at as high a quality as possible. Doing this however does not guarantee that you will not get any algae growing however it should reduce the likelihood of one occurring.

All algae have a food source. If an algae outbreak does occur the best thing to do in my opinion is identify the type of algae it is, identify what this type of algae feeds upon and remove its food source. Once the food source has been removed the algae will start to disappear.

There are also a lot of ‘quick fixes’ on the marketplace at present. Ones which promise to remove algae ‘magically’. Whilst I am sure that some of these do actually work are they just masking the problem and as soon as you stop using it the problem will re-occur. I personally think so. In my opinion the best thing to do is look after the aquarium correctly.

A lot of aquarists give up this hobby and the majority do so due to algae outbreaks. When thinking about setting up the aquarium they picture and aquarium which is always clean. They soon find out that this is not the case and go from outbreak to outbreak and eventually they get fed up and give up.

The internet is a huge source of information and fellow aquarists are always willing to help other aquarists. If you do experience an outbreak then the first thing to do is check all your water parameters. If there are any areas of concern then these should be rectified and hopefully the algae will go away. If not then the next thing to do is check the equipment to ensure that it is all working correctly and if required to be replaced has been.

If after doing this the algae is still apparent then pop to your local fish shop, speak to a friendly aquarist and ask their opinion. You will find that the majority of people are prepared to help out. If you do struggle then as said the internet is a source of great information. In this instance probably a forum or social community would be your best bet as you will be able to upload a picture of the algae where other hobbyists will be able to identify it and inform you of its food source. From this information you will be able to remove the food source from the aquarium and the algae should go away.

Of course you may get another outbreak. There are some aquarists who never have one – my dad John is one, he has never had an algae outbreak in his aquarium but then I have never seen another aquarium with water quality at the level he keeps his maintained at. Makes me jealous every time I see it!

The good thing about algae outbreaks in that each time you get one you learn something else about this hobby. This is now information that you can use to assist others if they get one and if you get another one then you will learn again.

As we always say – ‘in this hobby you never stop learning’.


Why Do Algae Blooms Occur In The Home Aquarium
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7 Comments
  1. I completely agree! Don’t use quick fix products they will only lead to more trouble.

    Instead look for the cause of the problem.

    ie Hair Algae: Elevated Phosphates and Nitrates
    ie Red Slime Algae: Elevated Phosphates (not Nitrate dependent)

  2. For a long time I have known that a spectrum shift in a light bulb will cause algae blooms. However, recently I came across a strange situation.

    I had set up a new tank with a refugium. The main tank was lit by 250watt 14k Iwasaki. The bulb was brand new. My refugium was lit by an one year old 65watt PC bulb. I had the typical algae blooms but not where one would expect. I started off my refugium with a very large ball of Chaetomorpha. During the cycle I had large quantities of diatoms and hair algae in the display but my refugium was clean. Both my micro and macroalgae were growing at a fast pace but in very separate areas. I cannot figure out why my refugium with such an old bulb was absolutely void of microalgae and growing my Chaeto at a fast rate. My main tank with very high flow and brand new 14 bulbs had massive amounts of hair algae. This leads me to believe that macroalgae can deter microalgae not just by out competing it of nutrients but also by something else. I’ve been around SW aquariums a long time and I can’t figure out what is going on.

  3. Hi.

    It is strange, isn’t it!

    The easy cop-out explanation is that the nutrients in the refugium have been taken up by the introduced algae and there is nothing left for the hairy stuff .

    So why is the display tank under the hairy attack? The bulb is new so there should be a correct spectrum and, in addition, I note that the bulb is 14K which, as you know, is more towards the ‘cold’ or blue, not lower down in the 6K or lower range where there could be more red, one colour that hair algae likes (as in sunlight). The circulation will be to its liking within reason.

    I could suggest detritus, dirty sand bed (if any), overfeeding, overstocking and all the rest. I note though that you are experienced so those are unlikely – so don’t be offended.

    One thought is I wonder if there is a very slow flow between the refugium and display tank. This would mean lesser exposure of all the system seawater to the algae.

    If you have a sump in addition could that be seeded with Caulerpa or whatever? That might help.

    Hair algae, even when starved of nutrients, sometimes is really obstinate and takes its time to depart. This may be because as it dies it again produces nutrients? The nitrate/phosphate may be gone or reducing.

    I’ll have to let my brain cell trundle along with this one! Maybe I’ll sit up in bed at midnight and shout ‘Eureka’ and scare my wife!

  4. very nice idea. i liked your blog very much and enjoy reading it again and again.

  5. Time to get 2 Siamese Sucker Fish for those hard to maintain algae tanks. 🙂

  6. This is one of my problems! Thanks a lot for sharing some information. This is really helpful.

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