Look at all dem sponges.

[ReefWitch]

I lifted the lid on my hob floss filter today to check it and found these dudes. (Photo is white light) I'm pretty sure they are harmless sponges but any second opinions would be appreciated.

 

[Rick's Reviews]

I lifted the lid on my hob floss filter today to check it and found these dudes. (Photo is white light) I'm pretty sure they are harmless sponges but any second opinions would be appreciated.

a general and consistent clean would help your filter work constantly, if it gets stacked up/ full of this stuff it won't work properly
At a guess this has not been cleaned for months to amount to build up.

However one good clean, remove it and scrub/remove as much as possible

 

[Rick's Reviews]

a general and consistent clean would help your filter work constantly, if it gets stacked up/ full of this stuff it won't work properly
At a guess this has not been cleaned for months to amount to build up.

However one good clean, remove it and scrub/remove as much as possible

You will be good for months

 

[ISpeakForTheSeas]

I lifted the lid on my hob floss filter today to check it and found these dudes. (Photo is white light) I'm pretty sure they are harmless sponges but any second opinions would be appreciated.

Yeah, those are sponges and harmless filter feeders- as mentioned though, it may not be a good idea to let them build up excessively in your equipment.