A few weeks ago, I noticed the following things happening with my 5 gallon planted tank:

  • Black hair/brush algae started showing up in my aquarium and growing on plant leaves
  • A lot of anacharis, which had been enjoying good growth, died
  • My red cherry shrimp started disappearing

I haven’t seen many pictures online of the kind of algae that I have. One website said that the black variety that I have is caused by low CO2 levels but they didn’t have photos, and I haven’t found other sources of information. The algae is firmly attached to plant leaves and doesn’t wipe or rub off.

I didn’t test my water when I first noticed this, but I did continue with my regular water change and did a few additional water changes too.

I got some otocinclus to eat the algae, but they wouldn’t touch it. Then I bought some Florida (American) flagfish. They eat it and have eaten most of it. Here’s some photos of the algae:

In some of the pictures, you can see some shrimp. That’s in older pictures. When I got the flagfish, there was one left, now they are all gone.

I’m still dealing with this and would appreciate any advice. Or if anyone can properly identify what type of algae I have. If it is a CO2 related problem, I’d have to think hard about getting CO2 equipment as I’d like to keep expenses low for my low-tech tank.


  1. I didn’t check the water parameters – I know I should’ve. Since the outbreak, I’ve gone through my regular and additional water changes. I also did a 100% water change and cleaned everything – the filter, the gravel, wood, etc…

    I use full spectrum (daylight) lights and turned the lights off for a few days. Then I turned it on for just a few hours a day. When I noticed my anubias suffering, I sped up the increase in the amount of light they received.

    Everything I’ve done – and I think some of them were drastic measures – seems to have controlled the algae

    I still have some anacharis in there and they’ve grown.

  2. Here are a number of thoughts. First, check your phosphates. If they are up, eliminating them will help starve out some of that algae. Your water may also have some iron in it. If you are making frequent water changes on a five gallon tank, you could be overdosing with iron. Light can have a lot to do with it as well. Old bulbs will typically be more favorable for algae growth. Try replacing the bulbs if they are old. Make sure that they are the proper Kelvin Temperature as well. Just having wattage is a minor part of the equation. If this is only a five gallon tank and the infestation is heavy, start over. I’m guessing you have a fifty five gallon tank and the five is a misprint. Anacharis can help control black hair algae but it is not a panacea. Too frequent water changes can eliminate beneficial bacteria, (nitrobacter, nitrospira, nitrosomonas)and cause a spike in your end result nitrate levels. High nitrate coupled with high phosphate can really enhance algae growth. I hope this helps.

    1. Thanks for the great advice Dave!!

      The tank is/was actually a mature (as in over a year) five gallon tank. I’ve since restarted the tank. I’ve concluded that the algae outbreak was due to new gravel I had introduced several weeks earlier – it was a laterite mix that just helped the algae outbreak.

      Since the gravel has been changed and the algae manually (cut-off), I haven’t had a problem since!!