DEFINE - What are diatoms, or brown algae?
Luckly, this algae is pretty easy to address. Diatom algae comes in a few forms. The first is a brown fuzzy form which kind of looks like dust bunnies. The second is a fine brown dust that covered your sand substrate, plants, hardscape, etc. It can build up over time looking like a thick brown layer.
General causes:
High organics (ammonia, nitrites) still floating around your tank
Immature aquariums (6-8 months or less)
Poor filtration design (looking at your sponge filters)
Silicates in a sand substrate or tap water
REMOVAL - How to remove those pesky diatoms
The methods we are about to mention will not prevent diatoms from coming back. We'll address that shortly. But here are a few ways to remove it from the tank.
Manual removal (fuzzy diatoms) - If you are dealing with the dust bunny diatoms, it can easily be sucked out with a water change and a siphon. Sometimes it will stick a little but then you can use a toothbrush to remove it by hand. This is the easier to the two types of diatoms to remove.
Manual removal (dust diatoms) - Since itsa dust algae, it can be wiped off easily. if its on your hardscape, use a toothbrush. If its on your plants, you can generally wipe if off with your fingers, but a toothbrush will work here as well. If not address for a while it can get pretty thick, and be stubborn to get off, so an algae pad on hardier plants, like anubias, can be used. We suggest wiping the tank down right before a water change so you can siphon out as much of the algae that is suspended in yourw atger column as possible during a water change. If diatoms are developing on yoru sand bed, use a siphon to cuk them up and/or stir p the san bed to bury the unsightly brown dust. With a cheap sand substrate, like play sand, the diatoms will continue to come back until all the silicates have been consumed from the substrate which can take months. This is one of many reasons to use products that have been designed for aquarium use.
Bleach dip - There is very little that can survive a cleach dip. Mix 1 part bleach to 20 parts of luke warm water. Sensitive plants, like crypts, dip fro no longer than 90 seconds. Heartier plants like anubias can be dipped for 150 seconds. Do no dip mosses and rinse REALLY well with dechlorinated water after the dip session.
Below is another example of fuzzy diatoms. Photo provided by ASG member Matt Robinson.
DILEMMA - Organics cause brown algae, but we need organics to cycle a tank.
Before we start solutions about this aglae, we need to talk about he dilemma. This is that diatoms develope generally due to high organics in the water column (ammonia and nitrites). Unfortunlety we need high levels of ammonia and nitrites when cycling a tank to develop beneficial bacteria. This is generally why we see this algae during the cycling process, and why its sometimes referred to as "new tank syndrome". There isn't much we can do about this algae during the cycling process because we don't want to process water changes... assuming you went with a fish-in-cycle. The only way to prevent this algae when cycling is to lower your light intensity to slow down the growth, or process a "dark start" where your lights are off for the entire cycling process. This only make sense if there are no plants in the tank. Check out the video below to learn how to process a fishless cycle and how to use the dark start method to prevent diatoms when starting a new tank.
Once the cycling process is over, we can then start processing water changes to lower organics. Also with having established the beneficial bacteria in our filtration this will prevent diatoms from coming back. The solutions we are about to cover are assuming that your tank has already been cycled properly and you have filtration set up properly. If you need help setting up filtration properly, watch the video below.
Solutions - How to keep diatom algae 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 filtration. If your tank is cycled, and you are still seeing this algae, we need to look at your filtration. If you have your filtration set up, you could have either crashed your cycle, or you don't have adequate bio-filtration. We want to make sure that we:
Have dedicated bio media to house our beneficial bacteria. We do not want to rely on our mechanical filtration (sponges) for this. Looking at you sponge filter users. We want to be able to clean our sponges our really well to remove rotting matter, like dead plant matter, uneaten food, fish waste, etc.
We need to ensure we are not cleaning out bio-media with tap water, as it can kill our beneficial bacteria. There are studies that show our bacteria can handle some amounts of chlorine for prolonged periods of time, but its best to just not risk it. Chlorine can kill our bacteria thus restarting our cycling process, which organics build up again in turn stimulating the development of diatoms.
We want to make sure our filter is able to turn over our water volume 10x an hour. Example: We have a 20 gallon aquarium, we want a filter that has a gallons per hour (gph) of around 200. This will ensure the filter is processing any ammonia and/or nitrites of out the water column very quickly, and not leaving them in the tank to float around. Again, if you are struggling with setting you your filtration properly, or would like a refresher, check out our filtration video above.
Solution 2: Dial in lighting. The two variables we have to change are PAR (intensity) and duration. I would suggest running 85PAR or below if your tank is not CO2 injected. And regardless of CO2 injection, I would suggest running a 8 hour photoperiod. No more or less. If you are injecting CO2 then you can blast your tank with a ton more PAR, but too much lighting in a planted tank is always going to cause algae.
Solution 3: Reduce your bioload. If your trilation is set up properly, and your tank has been cycled for a while, AND you are NOT showing any ammonia or nitrites, you tank is probably overstocked from an algae perspective. Just because an online fish calculator says you can put 5 large angelfish in a 20 gallon doesn't mean we should do it in a planted tank. The more fish in the tank, the more of their organic waste is being produced and is floating around the tank. Most of these calculators are designed with the fishes health in mind, not algae prevention. If you have no fish in your tank, you would probably not see any alage at all! Of course its a balance. We want some movement in the tank in the form of fish, but we don't want to pack our tank fill of fish. A good example of my mistake in the past was a 28 gallon I had with 2 large roseline tetra, a couple tiger barbs, a red tailed shark, some cory, some otos, a school of neon tetra and two rainbow fish. Sounds fun, but it was WAY over stocked. I was running a Fluval 305 at the time which was able to process out the ammonia and nitrites that went through it, but there was just enough organics in the tank to keep diatom dust algae around. Once got a larger tank, a 75 gallon, the brown dust algae (diatoms) subsided. Just be conscious that LOTS of fish can cause algae all on their own.
Solution 4: Water changes baby! There is nothing healthier for your tank than fresh water. You'd be surprised at how many people never change their water and just top off. As you are learning, free floating organics, or dissolved organic compounds (DOCs) is the main cause of diatoms. Processing large water changes will help remove any organics that you might have in your water. We recommend 50% water changes weekly when the tank is running fine. We suggest bumping it up to 75% water changes when we start seeing issues. Remember, if you are going to manually remove ANY algae from a tank, do it right before a water change so we can suck out as much of a algae in the water column as possible. That last thing you want to do is disturb something like brown algae, then let it all settle back into your tank. Keep up on your water changes.
Solution 5: Sometimes you just need more time. Tank maturity is really important. The longer your tank has been set up, and the more mature your plants are, the less susceptible your tank is to algae in generally, but specially diatoms. It can take 6-8 months for a tank to become mostly established. Tank that have been running for 1-2 year can easily outcompete algae IF they are running the ASG method. So if you're seeing diatoms, and you're running out methods, just stay the course. Your tank just might need some time to mature.
If you are new to the ASG method, check out our Part 1 series on YouTube here! We cover all the topics above in more detail.
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