Josh’s Guide To Freshwater Algae

We used to think that algae was caused by an excess of phosphates and nitrates in freshwater aquariums, however modern science and fertilising techniques have shown that this simply isn't true, the only exception to this is in heavily planted aquariums, where nitrates over 50ppm and phosphates over 10ppm will cause a phenomenon known as inhibition, which will cause plants to start decomposing at a microscopic level, releasing ammonia into the aquarium, this leads us on to the actual cause.

 

All algae is caused by the presence of light, and ammonia. The more light we have, whether it’s a source of natural light, or an aquarium light, the less ammonia is required to trigger algal growth. We need to ensure we have an appropriate amount of biological filtration for our aquariums, remember to clean your filters with old aquarium water to maintain the levels of beneficial bacteria (Chlorine in tap water is lethal to filter bacteria) and to make sure our filters haven't become clogged with waste.

It is important to realise that ammonia is present in all our aquariums, it is produced by our fish’s biological processes, waste, uneaten food, decomposing plant leaves, and bacterial death. An efficient, mature filter will quickly process that ammonia into nitrite, then nitrate through the nitrogen cycle before the algae has a chance to utilise it.

 

The specific kind of algal bloom is determined by light and ammonia plus an additional factor, fortunately for us, identifying the specific kind of algae will also help us identify the additional factor, which in turn, will help us address that factor and treat the root cause of the algae. Prevention is always better than cure.

 

Diatom algae comes in two forms, the first form is a slimy brown film appearing on the surfaces of our aquariums, such as on the substrate, glass and plants. The second form presents itself as thin brown threads. Both forms can be easily wiped away, and algae eaters such as Amano shrimp or oto cats will feed on it.

 

The additional factor which causes diatoms? silicates, which are introduced from substrates and rocks added to the aquarium, fortunately silicates are a finite resource which is why diatoms are often seen in new aquariums.

 

The Solution? Water changes and time, as the diatoms grow, they use the silicates to form an exoskeleton, increase your biological filtration and manual ammonia and silicate removal via water changes.

 

Green dust algae is a kind of zoospore which consist of a colony of individual cells capable of movement, they are most often seen covering your hardscape and glass in a thick, flat, green dust-like layer.

 

The additional factors which causes green dust algae? There are none, it is caused by an excess of light and ammonia.

The solution? Reduce your overall hours of light, remove any sources of indirect light such as sunlight on the aquarium, increase your biological filtration and manual ammonia removal via water changes.

 

Green spot algae is small, round green spots on hard surfaces, it is most often seen on aquarium glass, hardscape and slow growing leaves of plants such as Anubias. It is known as the algae of healthy aquariums and is seen in the vast majority of tanks.

The additional factors which causes green spot algae? Low co2 and/or low phosphate levels.

The solution? Consider adding a pressurised co2 system to your aquarium in combination with dosing phosphates, increase your biological filtration and manual ammonia removal via water changes.

 

Black beard is the bane of a lot of aquarium keepers because it is one of the most difficult to remove. It presents itself as small tufts of black, brown or deep red, in harder water it incorporates calcium into its growth which means the vast majority of traditional algae eating species won't eat it.

The additional factor which causes black beard algae? Fluctuating Co2 levels.

The solution? Consider adding a pressurised Co2 system to your aquarium, tap water is rich in co2 so allow fresh water to stand for a few hours to de-gas before performing a water change, increase your biological filtration, and use a carbon product such as Seachem Excel to spot dose the algae directly with a syringe to kill it.

 

Hair algae is one that the vast majority of algae eating species absolutely love, it presents itself as green-grey, long, thin, cottonwool-like strands.

The additional factors which cause hair algae? Low co2 and low flow.

The solution? Consider adding a co2 system to your aquarium, add a source of additional flow such as a powerhead or wavemaker, increase your biological filtration and manual ammonia removal via water changes.

 

Whilst not technically an algae, this is a type of bacteria that photosynthetic and a number of different species can appear in our aquariums, it often shows itself in freshwater as a film of blue-green, grey, red or black slime quickly covering any and all surfaces it makes contact with. It is also accompanied by an “earthy” smell. Cyanobacteria produces toxins which are deadly to livestock and plants so its spread should be stopped quickly, we used to think that cyanobacteria was caused by solely by low nitrates, however it has since been discovered that certain species thrive in high nitrate environments too.

 

The additional factors which cause cyanobacteria? High temperatures and low flow.

The solution? Add a source of additional flow to your aquarium such as a wavemaker or powerhead, and lower the temperatures to the lower range of what your livestock will accommodate, increase your biological filtration and manual ammonia removal via water changes. Test your nitrate levels, if they are low, less than 10ppm, then consider increasing them with nitrate dosing, if they are high, above 30ppm, then increase the frequency of your water changes.

 

Green water is caused by a free-floating algae that can be composed of multiple organisms, such as chlorella and flagellates, it is caused by an ammonia spike in combination with high light levels, improving the water quality afterward will not fix the issue, as after it has bloomed it can survive in low ammonia conditions.

 

The additional factors which cause green water? There are none.

The solution? Turn off your lights and completely black out your aquarium from any source of light, this can be achieved by wrapping the aquarium in thick towels or cardboard. Combine this with use of a UV unit will completely eradicate this kind of free-floating algae as it passes the ultraviolet light.

Thanks for reading and I hope this article can help dealing with any ongoing or future algae issues you may face.