DEFINE - What is green dust algae, or GDA?
Green dust algae, or GDA, is a dust algae that generally collects on your glass, hardscape and sometime even our plants leafs. This is probably the most common algae we see in the hobby. It should not be confused with an algae bloom, which is where your tanks water turns green. GDA should rub off relatively easy, and it preventative measure are not taken, can come back in a few days.
General causes:
Too much light (either from our aquarium light, or from direct sunlight)
Too much fertilizer
Not enough plant mass
High organics. The tank may be overstocked with fish and be producing too much ammonia, nitrites nitrates, before the filter can process them out.
REMOVAL - How to remove this stuff
The methods we are about to mention will not prevent green dust algae from coming back. We'll address that shortly. But here are a few ways to remove it from the tank.
Manual removal (scraping) - To get it off your glass/acrylic, you've got to get scraping. Make sure to use a glass or acrylic safe scrub pad. If you're looking for something cheap around the house, a flexible plastic gift card work great. For plants with thicker leafs, you can use the same scrubber that you use on your glass to rub it off your plants. Thinking specifically about anubias and Java fern as their leafs are a bit thicker and resistant to ripping. Just don't scrub too aggressively. To get it off hardscape, use an toothbrush! Its not like green spot algae, which you'll need something like a wire brush to get it off your rock work. The dust should brush off easily. Ideally, you'd want to scrub it away right before a LARGE water change and remove as much of the water as you can. DO NOT bush away GDA and let it float around your. It will just settle somewhere else and continue to spread.
PREVENTION - How to keep this stuff from coming back
I am going to say this in every algae article... we need to make changes to how we've designed our aquarium otherwise the algae will just keep coming back. The definition of crazy is: doing the same thing over and over, yet expecting different results. Do not rely on fish, algae eaters, snails, shrimp etc., to fix the design flaw that we've introduced into our tanks.
Solution 1: Check your nitrate levels. If they are too high, we can run into GDA. Start by looking at your fertilization method. If you are using the EI method, or an all-in-one like Thrive, you might be dosing too much. We see GDA when we have dosed too much fertilizer, and our nitrates have gone through the roof. Make sure to only dose enough fertilizer to boost your nitrates up 10-20ppm from where they normally sit with fish. This means if your tank is already sitting at 20ppm without fertilizers, you might run into GDA by dosing fertilizers. From there it might be wise to reduce your overall bioload to leave room for fertilizers.
But green dust algae generally means we just have too much fertilizer/nitrates and light. If you do not have a way to test your nitrates, we suggest this API Nitrate test kit. They are very easy to use and it will give us a window into where your fertilization and nitrates sit.
Solution 2: Water changes. We all know that water changes are the great equalizer if the water you are putting back is ideal. But surprisingly there are still many people that either don't process water changes, don't change out enough water, or don't process them frequent enough. Processing a 25% water change leaves 75% of the problem still in the tank. We suggest processing 50% water changes weekly, on a planted tank, to maintain the tanks health. If you run into a water quality issue, or algae, we suggest bumping up your water changes to 75% weekly. This will help reduce organics like ammonia, nitrites, nitrates, and/or fertilizers that may have built up over the course of a week, creating an imbalance. Remember, if you are going to manually brush away the GDA on your glass, hardscape or plants, do so before your water change, THEN siphon the water out of the tank. The last thing you want to do is disturb the green dust algae, and then let it sit in your tank. Keep up on your water changes, and process heavier, more frequent water changes during times of algae crisis.
Solution 3: Reduce your lighting! Sometimes more is not better. Balanced is better than excess in aquascaping. If you are NOT injecting CO2, we suggest you keep your lights PAR between 60-80. If you are injecting CO2, you can raise it up to 80-120 PAR. If you are injecting CO2 and seeing GDA and are above 120 PAR, then its time to dial your lights back. If you are injecting CO2, are around 80 PAR and STILL seeing GDA, then you'll want to dial back your fertilizer/nitrates a bit by processing heavy water changes. This will reduce the nutrient levels in the tank. If all this PAR talk is greek to you, watch our video below on lighting.
Solution 3: Dial in your lights spectrum. We see a lot new hobbyists buy expensive lights thinking that it will help their tank, but from the wise words of Yoda, 'With great power comes great responsibility". Just because your light is producing a lot of PAR, doesn't mean that your plants can use the spectrum you are providing them. Did you know that according to the University of Utah AND the University of Michigan, blue wavelengths suppress plant mass while red wavelengths increase plant mass. Less plant mass means less surface area for photosynthesis. More plant mass means more photosynthesis. If you have a (W)RGB light, we highly suggest reading our article on "Dialing in your programmable LED aquarium light". It will teach you which colors to crank up, and which to dial back.
And for those of you who decided to buy a Fluval 3.0 light, read this article - "What settings should I use for a Fluval 3.0 aquarium light". Fluval decided to get fancy and give you guys everyone BUT WRGB. So, this article will teach you which colors to crank up, and which to dial back.
Solution 4: Add more plants! This might seem counter intuative, but adding more plants can help soak up any additional organics or nutrients you might have floating around your tank. When we set up an aquascape, we want to plant as heavily as possible from the begenning. Faster growing plants are preferred over slower growing ones. This will ensure that the plants get established and mature before algae can get ahold of the tank. So, maybe you just need more plants. Check out our online shop! We've for you covered for all your plant need.
ADDITIONAL EDUCATION - How to use fertilizers
Fertilization plays a big role in GDA. If you are tossing fertilizer into your tank without knowing how much to dose, you could be stimulating GDA. If you are newer in the hobby, we suggest you check out our video on Thrive which is below. The video covers why we love Thrive, and how much you should be dosing! Spoiler, all you need is a nitrate test kit. 😉
If you have been using an all in one for a while, and want more control, we'd suggest trying out the EI method. With the EI method you mix your own fertilizer! Now I know that sounds crazy but its really easy. The reason we suggest the EI method for more advanced hobbyists is due to control and cost. Example: If your nitrates are already sitting around 20ppm due to livestock in the tank, and you don't want to dose more fertilizer because it has nitrates in it and can stimulate GDA, then you can simply mix a batch of fertilizer that doesn't have nitrates in it. Its that simple. This way the fish can provide the nitrates, and you can dose everything else like phosphates, potassium and trace elements. If you'd like to learn more about the EI method, watch the video below.
Now I know we covered a lot. If you have any questions about algae, reach out to us on our new forum! We can help you troubleshoot your algae issues.
