Green Dust Algae (GDA)
GDA appears as a fast growing, green film, usually on hardscape and the sides of aquariums. It’s easy to wipe away but will quickly regrow, sometimes overnight. The difference between GDA and Green Spot Algae (GSA) is that GDA forms a thin green film, with no formation of dots like with GSA.
GDA is often develops in tanks with low plant mass and excess organics, in tanks with high light and nutrient rich water, and is encouraged by warmer water temperatures.
It also frequently appears in tanks that are still cycling or in those with insufficient beneficial bacteria.
First, you should increase your plant mass so that your nutrients and light are being used. Maintain a regular maintenance schedule of siphoning detritus and changing water on a weekly basis to ensure nutrient and organic levels don’t get too high.
If you’re using pressurised CO2, consider if you are injecting the correct amount into your system.
Less severe cases of GDA can be treated easily with products such as LCA Carbon Plus or Triple B.
In severe cases, starving the GDA of all light sources with a 3-5 day complete blackout can be effective. Keeping nitrate levels low during this period until the GDA dissipates may also be helpful.
What’s the right amount – and can you have too much?
Most people will recommend your filtration should have a turnover of around 10x the total volume of your tank per hour.
So for example, a 100 litre tank should have a 1000lt/h filter running on it (if not 1200lt/h to make up for filter media/hose length reducing this rate).
This is to ensure good mechanical and biological filtration, providing the best foundation for great water quality. Debris/organics will be more likely to be removed by the filter, and beneficial bacteria in the filter will benefit from the flow. A larger filter also means more filter media, which allows for a bigger bed of bacteria to grow. It’s a win all around!
Many aquariums don’t have this level of filtration, relying on smaller, low-flow filters like HOB (hang on back) filters or underpowered canister filters. The problem with low flow, apart from poor filtration capabilities, is that nutrients and CO2 are not distributed evenly throughout the aquarium. CO2 exists even in low-tech aquariums, just in much smaller quantities.
While good flow is important in any aquarium, some considerations need to be made to ensure problems don’t arise.
So what’s wrong with higher flow?
It depends on how your flow is directed in your aquarium! If you have a narrow outflow directed at your hardscape and plants, they’re getting blasted with pretty intense flow.
A lot of aquarium plants aren’t used to these fast flowing conditions and will get physically stressed, especially those with delicate leaves which can get damaged. The stressed plant is weakened; damaged leaves get less support from the plant and start ejecting organics. Suddenly you have BBA!
The flow starts blowing microscopic bits of BBA around your tank where it looks for stable surfaces to grow on – usually slow growing plants like anubias and also your hardscape (especially driftwood). You’ll usually see it form on the outflow of your filter as well, where it can get all the nutrients it likes.
If your CO2 levels are unstable, the BBA will likely worsen as your plants struggle to adapt to the fluctuating conditions.
Your planted aquarium might be perfectly healthy otherwise, but when plants get stressed they will always attract algae!
So I need good flow - how can I keep the flow but fix the problem?
There are a few easy steps you can take. If you’re using a narrow filter outlet, changing it for one that spreads out your flow can be beneficial. For example, a spray bar or lily pipe will create a wider and therefore more gentle outflow than a single tight stream.
If you can direct the outflow, point it away from plants/hardscape/etc and out into unoccupied space.
If you have slow growing plants, delicate leaves or hardscape being affected by BBA and they’re in the path of your outflow, shift them somewhere else in your aquarium.
Remember, damaged leaves are not going to be repaired by the plant and will be leaking organics. The best thing you can do for the plant is trim off any affected leaves, which will let it focus on new, healthy growth.
Keep up with your fertilisation to make sure all your plants are growing healthy and without stress, and make sure you’re injecting enough CO2. Whether you’re using pressurised CO2 or you have a low-tech system (which still has CO2 in much smaller amounts), you need to make sure your water circulation is adequately dispersing the CO2 throughout your aquarium.
You can keep a high flow rate in your aquarium, just watch where it’s going!
From The LCA Team
Every Solution For Your Aquarium
Spirogyra generally grows on plants in dense, medium to long curling threads.
It is usually caused by low CO2, excess organics (especially iron), too much light or poor water circulation.
To treat, start by manually removing as much as you can. If using pressurised CO2, reassess the amount you are injecting to see if it is sufficient. Clean your filter to reduce organic waste, and while the spirogyra is present, increase frequency of water changes – weekly if you are not already doing so, 2x per week otherwise.
If your photoperiod is longer than 7 hours or your lighting is particularly intense, reduce your schedule to 6 hours and observe over 2-3 weeks for any changes.
If you are using fertilisers containing Iron, consider adjusting your dosage rate or using a product containing less iron to reduce the levels in your aquarium water.
If circulation is poor, you can add a circulation pump, upgrade to a more powerful filter or trim overgrown plants to allow for better flow. Trimming plants has the added benefit of creating more bushy growth.
Treatment with products such as LCA Carbon Plus or Triple B is effective in weakening or inhibiting algae growth and may be suitable for combating spirogyra as part of a total treatment plan.
Cladophora grows in short, green filaments that are quite tough. It typically attaches very firmly to hardscape in the aquarium, such as wood or stone. It can also grow throughout plants such as moss and carpeting species, creating a tangled mess.
Some hobbyists will purposely keep Cladophora, as it can look appealing when added to hardscape and carefully managed. In fact, marimo moss balls are a type of cladophora and are widely kept in freshwater aquariums.
If not intentionally introduced, cladophora can be caused by slow water circulation, areas receiving no flow and intense light, areas overcrowded by plants or decaying undergrowth. Generally speaking, low flow encourages this algae to form.
To treat, first manually remove as much as possible, which can be difficult. For mild cases, you can spot-treat with hydrogen peroxide misting or products such as LCA Carbon Plus or Triple B.
Any old or decaying growth should be pruned or removed. Similarly, overgrown plants should be trimmed and tops replanted to help with flow. If lighting is intense, consider adding more plants to use the light available.
Increasing growth rates of your existing plants is recommended by optimizing your pressurised CO2 (if using), and adjusting fertilisation rates if required.