Algae in your Freshwater Aquarium? Identification. Treatment. Prevention.

So, you have algae? There’s no shame in that, we all have algae. Pull up a chair and let’s talk it through.

I wish I could tell you that I am able to give you a cool, logical discussion on algae. But I am a little obsessive and it really, really bugs me to see my tanks get a visit from the algae monster. In truth, though, it is really a matter of when there is too much algae or the wrong sort of algae.

A guide to help you with freshwater algae identification treatment and prevention

Obsessive or not we have to accept that as aquarium owners we are bound to play host to this stuff most of the time and the sensible approach is to learn to recognise whether our algae is something we can live with or something that if left unchecked will ruin our tank.

There are five things to look at here

  • Identify your algae – a list of algae types with specific cures where they are known.
  • General recipe to help avoid algae.
  • Tools to help fight algae.
  • Algae eating critters.
  • Chemical cures - a warning and a promise

Avoidance of algae is really the most important, as if you don’t cure the reasons algae are doing too well in your aquarium you can pull it, scrape it or poison it as much as you want and it will still come back.

Types of Algae

First, though, let’s get to know the enemies. It is so important that you identify what algae is your main problem as it will give you clues as to how to deal with it.

I have tried to list all the common types, but I’m sure you have examples that I’ve missed. I would really like to get feedback on this, especially if you can send us pictures of what you are dealing with.

Brown Algae (diatoms)

Blue-Green Algae or BGA (cyanobacteria)

Green Hair Algae (GHA), Thread Algae

Staghorn Algae

Green Water

Green Spot Algae (GSA)

Green Dust Algae (GDA)

Black Brush Algae (BBA)

Water Surface Algae

Recipe of tank maintenance to keep algae to minimum

I think there are two real types of algae issues. Those in planted tanks and those in tanks where the fish are the main feature. The reason things are different is because planted tanks tend to have maxed out lighting, carbon dioxide, and fertilisers. This solves some algae problems and causes some others.

I have references at the end which give great info on planted tank algae management.

In a fish dominated tank things are simpler in a way and you can focus on reducing algae in several ways:

Bob's Algae Checklist
  • Keeping the number of hours you have your lights on low. More than 9 hours will encourage algae.
  • If you’re planning a tank, put it out of the way of direct sunlight. One of my tanks gets 30 minutes of sun a day, if I don’t close the shades I will get extra algae.
  • Change at least 25% of your water once a week, vacuum any dirty gravel as you do.
  • Clean your filters once a month (more in a heavily populated tank).
  • Always dechlorinate new water added to the tank.
  • Feed just what your fish really need.
  • Jump on small algae problems before they get out of hand.
  • Keep the fish population well below recommended limits.
  • Try not to disturb your gravel unless you are cleaning it, there’s a lot of much in there that can trigger an outbreak.

If you follow these steps, at least when you get a bad algae outbreak you can know it wasn’t through neglect. Well maintained tanks get algae but poorly looked after ones get a lot more.

Algae Fighting Tools

You really don’t want to let algae get too established anywhere so it is sensible to

  • Clean your glass weekly
  • Vacuum your gravel as you water change
  • Take out and clean rocks with even a hint of the really bad algae types
  • Prune badly affected leaves of plants and discard the whole plant if its beyond hope

These are the tools I use. Other brands might be available as well…

Algae Eating Critters

I believe this is nearly your last step in the fight. Not because they don’t make a useful contribution but because most of the other cures can be used whatever fish you are keeping. However, whenever you add new creatures to your tank you should work out if they match your existing fish, your water, your tank size etc.

Another thing to remember is that different critters eat different algae and I don’t know of any that eat everything. I have a lot of algae eating species in my planted tank but I still have algae and they completely ignore the Green Hair Algae that bothers me most. I know in some tanks the same animals eat the stuff.

My point is your algae eaters can be a big help but not a cure and they must fit your system.

Here is a list of some contenders.

Siamese Algae Eaters (SAE)

Bristlenose Pleco, Ancistrus

RubberNose Pleco, Bulldog Pleco

Otocinculus, Otos

Hillstream Loaches

Twig Catfish

Chinese Algae Eaters

Nerite Snails

Malaysian Trumpet Snails

Apple Snails


Chemical Cures

This will be the topic of another article. The first reason is that there is so much scope for things to go wrong and so many warnings that I can’t just fit it all in a paragraph. The second is that they do nothing to solve the underlying problem that caused your algae.

I will cover shop bought algaecides, hydrogen peroxide, organic carbon overdose and nutrient balance. If you do some of these wrong and you can kill all your fish and plants.

Closing Thoughts

I really wish you luck with the algae. I know it can hit the most fastidious fish keepers. Let me know what tips help you and what has been a flop.

Further Reading

Leave a Comment:

Add Your Reply