Red flat creatures in the back panel filter

[roman94]

Hi lads,

I just spotted two red flat sponge-look like guys in my skimmer chamber. It’s the very first filtration chamber in my 320L tank. Can you help to identify this? They are 1x3” and +/- 3mm thick. The tank is 2,5 yrs

 

[MasonK24]

thats a sponge, a good sign of a healthy tank. i have quite a few. they look cool in my opinion.

 

[vetteguy53081]

Red photosynthetic plating sponge.

 

[MasonK24]

Red photosynthetic plating sponge.

i would say its non-photosynthetic with it growing in a sump chamber. ive had one just like it for 3 years growing in the dark.