Brown Algae (diatoms) – light brown dust appearance. They are common in newer tanks and will normally go away after a month or two. The best thing you can do during this time is clean your substrate, and maybe do an extra water change here and there. Most algae eaters will also help clear up diatoms.
Blue-Green Algae (cyanobacteria)- Not an algae, but we all call it an algae so lets add it to the list anyway. This one grows in thin layers and has a slimy appearance. Usually it is a bright green, but it can also be brownish red. This one is a pain… It can be caused by poor circulation. Black outs are a common approach because even though it’s a bacteria it still photosynthesizes. You can also use antibiotics containing erythomycin.
Green Hair Algae- This one is my personal nemesis. It can show up in small little clumps, the occasional strand on hardscape or plants, or completely infest the entire tank. If left alone it will spread! Typical causes are Co2 imbalance, too much light, and of course poor circulation. To fight it off it’s best to start by manually removing as much as possible. Increase frequency of water changes and try to find the cause. For particularly bad cases I have found hydrogen peroxide to be the most efficient way to kill Green Hair Algae. This will be a slow and steady battle.
Green Water- This one is typically an easy one to fix. Normally it’s caused by simply not doing your water changes often enough. It can also be caused by too much light and/or feeding your fish too much. It’s more common in tanks that do not have live plants to out compete the millions of little algae particles floating around. So simply adding some plants and doing a few water changes is usually all it takes.
Green Spot Algae- Dark green spots usually found on the glass. They can be difficult to remove with magnetic cleaners, but a metal bladed scraper will take it off no problem. If you do have some on your plants just prune the infected areas. Usual cause is high light. Regular water changes and cleaning infected areas is normally all it takes.
Black Beard Algae- BBA can be caused by too much light, no Co2, Fluctuating Co2, poor circulation, and high pollutants in water. To fight BBA I recommend improving circulation, fertilization, and making sure Co2 levels are stable and/or present. Start by removing any leaves with BBA on them by simply cutting them out. Use a toothbrush on any hardscape to remove and follow up by siphoning the dislodged BBA. You can then go through and spray any particularly bad areas with liquid carbon (such as excel). BBA will start to turn pink or red as it dies off. Once this happen remove and siphon again.
Preventing algae can be done a number of ways, but here are a few practices that I find particularly useful.
Keep your aquarium away from windows. Natural lighting can definitely cause algae outbreaks.
Keep your lights on for no longer than 9 hours. For more intense lights you may have to dial it back even further.
Always dechlorinate your water.
Change at least 25% of your water every week.
Eliminate algae as soon as you see it, especially with the more invasive ones!
Don’t forget to vacuum your gravel.
Prune badly affected leaves.
Siamese Algae Eater- These grow a bit larger reaching about 6”. They are especially helpful when it comes to BBA.
Plecos- Not all plecos are created equal! Many are carnivores, others eat some algae, and a few eat a bunch of algae. Research the pleco you want before assuming it eats algae.
Otocinclus- A store favorite for sure! These little guys/gals will munch on brown and green algae. They’re friendly and won’t cause problems with any of your other fish.
Chinese Algae Eaters- These can be a bit aggressive and I would only recommend them for tanks that have tougher fish. They also reach about 11”
Nerite Snail- Eats a ton of algae, including green spot. They come in all kinds of varieties and cannot breed in freshwater.
Shrimp- There are quite a few options here. Great for eating algae, especially amano shrimp. They will not do much for your glass though.
There are tons of other algae eaters that can help you with keeping your tank algae free, but these are just a few of the more common ones you will come across. I do not recommend trying to fight algae with a clean up crew though - finding the cause is always the best solution.