Off to a bad start

[Evil1]

 

[Tahoe61]

Hello everyone,
I'm new to saltwater and have been reading threads here quite a lot. Unfortunately, I believe I have gotten myself in over my head.
For starters my tank is a 25g IM lagoon. I turned pumps on in early April with first inhabitants in mid May(5 months). Dry marco rock and live sand.

Starting about a month back I was starting to see hair algae sprouting around the tank, around the same time Coralline started to replace the green film algae on the rocks. Quickly followed by red cyano slime, or at least I assume that's what it is. Starting about two weeks ago it began ramping up rapidly to the point it's out of control. It's covering most of the sand with cyano and a large portion of rock along with hair algae growing on the few zoanthids I have and some of the snails. This coincides with my Nitrate levels nosediving from floating around 5-7ppm in August and prior to undetectable on my last two tests (last Thursday and Today). Water changes 5g every Friday though I skipped the last one due to low nitrates.

Early last week, I reduced my lighting by two hours and from 60% intensity to 40%. Grow with Glow preset on AI blades. They now come on at 9am ramp up till 10am and dim down starting at 3pm till off at 4pm. I have moved my Ecotech MP10 to try to create more turbulence across the rock and increased it's speed.

Despite my efforts, this morning is the worst it's been possibly because no WC on Friday? Cyano covering almost all the sand and about 50% of the rock. Unfortunately, I didn't think to take a photo before I tried to remove a lot of it.

How bad is this problem? Any advice is appreciated! I can provide more info if needed. I apologize if I've given too much already.

Did you change out the stock return pumps, if not I would.
I found that 2 MaxiJet 1200 work well in the IM 25. They are a decent price on Amazon.
Honestly it's a harder tank to get the flow right, it's the foot print.

 

[FrugalReeferJon]

 

[Piotrek]

A 72h complete blackout with covering the tank with a blanket could help. Are you sure you are not overfeeding your fish? I see 2 clowns, is that all? If yes, you can try feeding them very little 2-3 times a week only.
Also are you steering up the sand during water changes? If not, steer it up a bit and make it release that cloud. It will help you prevent the accumulation of detritus and stuff in it.
If your NO3 and PO4 levels are ok, you can skip the water changes for a couple of week, feed little and check if that helps.
Adding some microalgae for a while to help cleanup the tank does the job as well. You can easily remove it later. PO4 absorbers might also help - I've run my first 10g with seachem phosguard in the system all the time. Now I just add a bag for a few days whenever PO4 rises too much.