Purple/black algae

[TissueTenant]

In my 5 gallon aquarium, I have this purple-ish algae growing over everything. I suspected that it might be cyanobacteria, but it doesn't have a smell and it's not cyan coloured. I tried a 3 day blackout, but it didn't have any effect at all on the algae. If I rub it, it comes off as a sheet. I'm more curious about what it is than how to get rid of it, since I know that manual removal and water changes should help.

 

[Colin_T]

Blue green algae (Cyanobacteria). It comes in a range of colours including dark blue, dark green, black, brown, red, purple, pink and loves nutrients, red light, slow moving water, and low oxygen levels.

Do a 75% water change and gravel clean the substrate every day for a couple of weeks. Try to physically remove the slimy stuff when you do this.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

Clean the filter if it hasn't been done in the last 2 weeks, but don't clean it if is has been running for less than 2 months total. Wash filter media/ materials in a bucket of tank water and re-use the media. tip the bucket of dirty water outside on the lawn or garden.

Increase water movement and aeration, especially around the bottom of the tank.

Make sure the light has a temperature around 6500K (cool white).

You can remove the ornaments and hose them off outside and it can help slow or stop it coming back.

Reduce the amount of dry food going into the aquarium.

 

[GaryE]

I have had that appear, but identification is an issue. I believe the black/purple one to be a Cyanobacteria. The one I get here can come in a couple of colours, and black/purple has only shown up once and not stayed long. In my affected tanks, it is a dark green form.

It doesn't always have the characteristic smell.

I do week long blackouts to knock it back. It's supposed to dislike flow, but it grows well on filter outlets here. My variety of cyano doesn't read its own press. Make sure the filter media isn't clogging, and check what your substrate is. I have a type of play sand I bought that feeds cyano blooms in every tank I used it in. I can have 2 tanks side by side with different substrates, and the cyano will carpet the white sand and not even appear on other types.

At least it's only a 5 gallon. They're generally easy to clean and manage, although I find the small volume leads to fast water quality issues. My water change schedule for the 5s I raise young fry in has to be rigid.

 

[TissueTenant]

Thanks for the advice! I appreciate it