my HOB refugium question

I had bought an 8 gal hang on back refugium from this guy he had on his 125g reef tank. When i picked it up he had told me with his auto top of filling up his sump, it would cause his skimmer to overflow so he turned it off and just relied on the refugium. There is a few inch miracle mud sand bed, and it looks like 7/8" fish waste on top of that. (You can see the fuge bottom in PIC)

My question is should i just syphon all that waste out, scoop all the mud out, replace with live rock or rubble, or leave it. My nitrates are up, but in the ok range. There is cheato in there, but getting small algae blooms..

 

I never experienced with mud but i would siphon it out and use rock rubble.

 

Yeah that's what I was thinking. It looks like theres a bunch of (crap) on the floor of it. However there are bristle worms making there way threw it all. I just don't know if i would be discarding good bacteria vs. bad..

 

definitely siphon off the waste. If it were me I would replace the mud while I was at it.

 

Ok i can syphon out that waste, should i take out the mud and replace, or just add LR rubble, and larger LR peices?
The guy i bought it from had his tank set up for 7 months. I did hear of replacing the mud after some time.
I do have a DSB in my DT now.

 

So I performed the joyus task of cleaning the sludge out of the fuge last night. After cleaning out as much LR rubble, I shop vac'd it all out. Man what a job! I tried wiping all the crap out of it, but left some mud muck behind. I didn't want to start flowing the cloudy water into the DT, so i left it settle overnight and today. It still looks like there is some left over settled mud. Will this little bit hurt that much, or should i try and get that out? i just added a bag of carbon back there too a few days ago. Should i add more? I have about a baseball size or a bit smaller.