Updated: Apr 26, 2021
So you've got the dreaded Black Beard Algae (BBA). Well, we've got you covered.
Below are the top 3 things that contribute to BBA.
#1) CAUSE (Most Common) - Too little, or fluctuating CO2: BBA is seen in a lot of planted tanks that are not injecting CO2. Why is this? Because a tank will naturally have around 5ppm of CO2 in them at any given time. Once the lights kick on and the plants start photosynthesizing, the plants start to use up that available CO2 and you can run into an issue where you have too little available creates a condition for BBA to thrive in. An example of fluctuating CO2 can be when using a DIY system. Most use something like yeast and sugar to produce a chemical reaction that creates CO2. One of the many issues with this DIY method is the yeast starts out strong creating CO2, and as there is less and less sugar available, their output starts to taper off, having it produce less and less CO2 over time. This fluctuation can also cause a depletion of CO2, again inviting BBA to take over.
#1) FIX - If you're not injecting CO2, then we recommend that you start! It's that easy. If you follow our CO2 method and you've dialed in your pressurized CO2 system, you'll never have to deal with BBA. Done and done. If you are injecting CO2, you probably are not injecting enough, or your method of injecting isn't keeping up. Remember that you need to obtain a 1.0 PH drop (Example, from 7.3 to 6.3) prior to your lights coming on to have your CO2 at that optimal level of 30ppm PRIOR to your lights kicking on. If you are not achieving that, turn up your CO2. If your CO2 is to the max, then you need to look at a larger ceramic diffuser as yours might be too small and the bubbles it's creating are just shooting to the top and out your tank... or look into a reactor.
#2) CAUSE (Rare) - Too much CO2. We can sometimes see BBA when the concentration of CO2 is too great. For example, if your diffuser is in the corner of your tank, and you're not getting proper water circulation, CO2 saturated water can build up in the corner cause BBA to grow around it... even on your diffuser! This is rarer but can still happen.
#2) FIX - If you can, either add a powerhead to increase circulation in the tank or position the outlet of your filter to shoot water in the direction of your diffuser. Overall, you just need a little more circulation in the tank. Not too much because of #3.
#3) CAUSE (Rare) - Too much circulation. BBA really loves REALLY high water movement. Now I'm not talking about water trickling out of a hang-on-back (HOB) filter, but we're talking about putting a massive powerhead in a 30-gallon tank. We will sometimes see some BBA actually growing on the power. Now we are not sure why BBA like to grow on the powerhead, but we do know that it likes those high-flow areas.
#3) FIX - Just slow it down. If you need to the circulation due to #2, just get a smaller powerhead or try to get a powerhead that is adjustable. I would only suggest powerheads in a tank that has 75-100+ gallons. Most tanks smaller than that have enough flow when utilizing a canister filter with 10x turnover per hour as we recommend. Now you understand why we do!
Last but not least, just make sure you are processing your 50% water changes weekly. Dissolved organic compounds (DOC), or to simply put it, crap building up in your tank can cause BBA as well. Make sure you are waving your hand against the substrate to kick up any detritus that might be sitting in your tank. You don't want those contributing to the three issues above.
WHAT IF YOU CAN'T RUN CO2?
There are 3 things you can to do help make sure you're tank isn't running out of naturally available CO2
Create more surface agitation - The best thing you can do is create some ripples across the water surface. Your plant mass is basically depleting your natural levels of CO2 and the ripples, not splashes, can help replenish more CO2 into your water column. I generally achieve this with the outlet of my canister filter. If you have the outlet closer to the surface, it will cause a small rippling effect which works perfectly. Again, no slashing or white water needed. You'll get extra points if you're running a surface skimmer as well. The oil sheen on the water surface can prevent gaseous exchanges.
Decrease the intensity of your light - If you can, either dim your light, or raise it up a couple of inches. Either will reduce the amount of PAR your light in producing, slowing down growth, or the use of naturally available CO2
Give your tank a nap - I know this sounds funny, but turning off the lights mid-day for 2 hours will shut down photosynthesis and allow natural CO2 levels to replenish... with proper surface agitation.
Utilize glutaraldehyde - (sigh) I'm not proud to recommend this, but something like Seachem Excel is an algaecide and will kill and can prevent BBA in tanks that are not injecting CO2. The reason I don't like recommending this is because we're really not addressing the issue of CO2 depletion, we're just killing the BBA. That and you'll be tied to buying bottles of this stuff delaying you saving up for a pressurized CO2 injection kit.
HOW DO PEOPLE GET AWAY WITH NOT INJECTING CO2
The only way people are able to get away with no CO2 injection is if they have a large enough body of water, that when plants are photosynthesizing, they do not utilize the entire 5ppm of CO2 that naturally occurs in the water columns. Surface or water agitation can also help including more CO2 back into the water offsetting what the plants are using. They are also probably using a low PAR light, cause the plants to grow SUPER slow. In addition, they probably have really slow-growing plants like Anubias, Java Fern, epiphyte plants in general. This is why they are considered beginner plants. They are hardy and slow-growing. So don't let someone fool you by saying "I don't inject CO2, so you shouldn't as well". They have a well enough understanding of their tank's CO2 demand and can get around it. Regardless, CO2 injecting is ALWAYS going to help keep your plants thriving.