what is this

[Ineedclownfish]

i think this is coraline algae but i am not sure so ca anyone tell me?
it used to be green but now it is purple with tiny hints of yellow

 

[blaxsun]

It looks like a thermostat...

 

[T-J]

It looks like a thermostat...

It looks like a thermometer.
Also, it's likely algae growing on the suction cup. Does it brush off easily?
How old is the tank? Typically coralline algae doesn't change colors. Do you have something in the tank that could have seeded it?

 

[j.falk]

Definitely a thermometer.

 

[Sleeping Giant]

 

[Nano_Man]

Yep tells you the temperature

 

[Ineedclownfish]

Definitely a thermometer.

i mean the things on the suction cup

 

[Cell]

You can barely see whatever it is in that photo.

 

[j.falk]

i mean the things on the suction cup

Rub your finger over it. If it's coralline, you won't be able to get it off easily. It'll feel hard/crunchy. If it's a regular type of algae, it'll rub right off.