Red Stains in Filter Sock?

[habanerosky]

For about a week I’ve noticed this red material in my filter sock. I’ve been changing it daily as it looks like this after <24hrs.

The only recent issue is that we lost power for 2-3 hours the other day. I had a bacteria bloom that lasted about 36 hours (UV light cleared it up). I think the bloom had something to do with the power outage. However, this red in the filter was showing up before and after this.

All my fish and corals seem totally fine, water is now crystal clear. Anyone know what this red could be?

Tested 2 days ago:

Salinity 1.027
Alk: 8-9
Calcium: 430
Mag: 1275
PH: 8-8.3
PO4: 0.08
NO3: 6.4
Ammonia: 0

 

[exnisstech]

Looks like mine when I blow cyano of the rocks.