Red algey as back help. Also new sump setup

[juboy27]

Hi I have a 3 ft tank with a new sump system. The main tank has been running for just over a year now. The past 2 months i have been suffering from red algey build up. its red but almost brownish tinge i have been doing my water changes once a week and checking my water parameters one of the readings that i was concerned about which has remain at 0 are nitrates. If anyone can suggest a natural remedy i e filtration that would be nice rather than using chemicals in the tank i will post some photos of the tank and sump to see what you think.
I'm still only an amateur and learning 1 day i hope to get some advice back.

 

[juboy27]

 

[juboy27]

 

[juboy27]

 

[juboy27]

 

[juboy27]

Update well I have had a good clean out of all the crap in the tank to day. I moved all the live rock 2 one side and hooved all the crap up out of the crushed coral boy was there a lot of crap. I i think this might be the cause of the problem. Only time will tell.