Strange 'flakes' of algae/bacteria

[bearman88]

Hello R2R. I restarted my RedSea Reefer 250 about 4 months ago, and things are going well. I did a restart due to a long fought dino battle.

Anyways I have noticed on the past 3-4 water changes that when I turn my return pump back on after the WC, these weird flakes which at first look liked decomposing meat started flying around. I had lost a couple fish mysteriously after the restart so I figured they were the remains of the fish an shrugged it off.

But there seems to be more growing. Last night I looked around my return pump (see photo) and that is where the source seems to be. It's some kind of yellowish algae/bacteria.

My maroon clown is happy, (he's all I've got atm), coral are happy and growing. Bio load is very low.

1) Any ID on the junk?
2) If I remove the bacteria block (this is old, I cleaned it and replaced from old tank - it's very brittle and mushy), can I just put the original sponge back and throw in some Life Rock in sump for bacteria area?
3) Could it be from NoPox? Reading around the forums, the slime could be caused by nopox.
4) Should I just try to suck it all out and clean out my sump really well? I've noticed this junk is stuck inside my skimmer, and reactor pumps.

Parameters:
Temp: 77.4
Salinity: 1.025
pH: 7.9
dKH: 10.0
nitrate: 0.75ppm
phosphate: 0.11 (right before WC and when I had stopped dosing nopox over vacation)
Calcium: 420
Mag: 1180

Thanks!

 

[T-J]

What I see in the sump pic appears to be just detritus settling. When you do your WC and restart the pump, I'm guessing it gets disturbed and pushed out into the tank.
I could be wrong, but that's what it looks like to me.

 

[T-J]

Also, I see you have metal hose clamps that are completely rusted out. You need to get that metal out of there!