Anyone know what algae this is?

[Stan510]

I've posted that BGA can kill fish if they ingest it..mostly bottom dwellers such as Corydoras,in the past right? Nobody agreed. "Oh,it's not harmful to fish". Colin is the first person to agree and as such must be a genius fish keeper too.
Many ways to deal with it. Slime remover ( but it can come back,its not 100% for 100% of the time you have the tank set up) but its just a start. Cleaning the whole substrate and filters often will get rid of it mostly. Along with weekly water changes. Basically,raise the level of health in the water..changes,aeration,go easy with the food- resist over feeding the fish.
Leave the lights off for a few days can also help. That and blue slime remover will do the job.
But!..if the conditions of what fed the algae dont change..it will return one day.

 

[Spyro]

I've posted that BGA can kill fish if they ingest it..mostly bottom dwellers such as Corydoras,in the past right? Nobody agreed. "Oh,it's not harmful to fish". Colin is the first person to agree and as such must be a genius fish keeper too.
Many ways to deal with it. Slime remover ( but it can come back,its not 100% for 100% of the time you have the tank set up) but its just a start. Cleaning the whole substrate and filters often will get rid of it mostly. Along with weekly water changes. Basically,raise the level of health in the water..changes,aeration,go easy with the food- resist over feeding the fish.
Leave the lights off for a few days can also help. That and blue slime remover will do the job.
But!..if the conditions of what fed the algae dont change..it will return one day.

That really depends on what type one has in their tank.
Vast majority of cyanobacteria are non toxic. Only few types are

 

[Bruce Leyland-Jones]

That really depends on what type one has in their tank.
Vast majority of cyanobacteria are non toxic. Only few types are

Fair point, but unless you have the means to determine exactly which species of cyanobacteria it is, it's usually safer to treat it as the toxic variety.
Here in the Lake District, we often get blue algae blooms, (low oxygenation, plus fertiliser run-off, etc.), and warnings sprout up telling people not to go into the water and to keep their dogs out...and this is in a lake/mere/water*, not just a small tank.

Whilst there are effective chemical means to address this issue, it will return unless the actual causative factors are addressed, namely poor tank maintenance.

EDIT: *There is only one Lake in the Lake District!

 

[Byron]

Cyanobacteria (which is what this is, no doubt) is caused by organics in the presence of light. The only safe method to deal with it is to reduce the organics. Light blackouts will work short-term, but if the organics are not reduced the cyano will only return when the light is restored.

Do not dump chemicals into the tank to "deal" with this, they are all harmful to fish, and possibly plants.

Do large water changes, vacuum the substrate thoroughly at each, keep the filters well cleaned (all that dark brown/black gunk is organic matter), do not overstock, do not overfeed, control the tank light, have live plants (floaters as always are superior here)...any of these factors. Also, I eliminated plant fertilizers and reduced the light period when I dealt with this in one tank. When it was obviously gone, after a few weeks, I recommenced the plant fertilizers. It never came back.

 

[Spyro]

Fair point, but unless you have the means to determine exactly which species of cyanobacteria it is, it's usually safer to treat it as the toxic variety.
Here in the Lake District, we often get blue algae blooms, (low oxygenation, plus fertiliser run-off, etc.), and warnings sprout up telling people not to go into the water and to keep their dogs out...and this is in a lake/mere/water*, not just a small tank.

Whilst there are effective chemical means to address this issue, it will return unless the actual causative factors are addressed, namely poor tank maintenance.

EDIT: *There is only one Lake in the Lake District!

Yup.
I meant more as in there are thousands of different kinds of cyanobacteria that are all called BGA.
Some are toxic and some are not.
Some bloom in presence of organics: some bloom in environment lacking Nitrates, some will be just fine without light and others will be hampered without light.

Fishkeepers arguing about whether they are toxic, what works and doesn't work against BGA is like bird keepers arguing whether corn is too big for birds to eat and if birds should be feed meat or not.
It really depends what bird one has that they call bird. One might have finch, other a chicken and 3rd an eagle; but they are all birds.

Success or failure in dealing with BGA, conditions it blooms in and whether it's toxic really depends on which one of thousands of different kinds of cyanobacteria individual has

 

[Avel1896]

I'd like to add that every single tool/accessory used in a problem aquarium, must be disinfected carefully, in order not to bring any mess back in the tank

 

[Stan510]

Sand in aquariums is prime habitat for BGA..it is like a chef for that particular algae. Better to use gravel or made for aquarium plants soils. Just use fine sands as filler in front.
Mother nature can get away with even finest silts...but that doesn't translate to healthy aquariums over all.