What are you using for water change? What are you using for topoff? If u are not using clean ro/ di then u are importing so bad stuff. Remove livestock. I would syphon the sand to get as much of it off the bed. Then i would remove all rockwork and scrub and rinse with clean satwater. Then stir sandbed and allow the filter to remove suspended material. Again syphon sand as heavy stuff will fall to bottom.
So water level is at a 2/3 now, clean tank and filter areas,pumps. Sump etc. Change all media.
You have exported 75% of bad stuff. Dont put it back with bad water or additional nutrients
Add rocks back and be sure there is good flo around and thru rocks. Now u can use the chemi again
I can lend you my sea urchin if you want
but that algae will come back again,
it looks like you're running your lights for too long, you not using RO+DI water and you don't have proper filtration
Don't panic. You need to consider your bio load and cleaning crew.
1: how many gallons is tank complete with sump if any?
2: how many fish are in system?
3: of those fish how many are grazers (eat algae)?
4: How often do you feed and what do you feed?
5: how often do you test?
6: what does your cleaning crew consist of?
7: are you using RO/DI water ALWAYS now?
8: do you have a sump, refugium?
9: what algae do you have if you have sump and or refugium?
10: do you use a reactor for GFO or Bio pellets (nitrate/phosphate removers)?
11: whats your level of commitment to your tank?
Once you answer these questions ppl can really help you.
why invest in uv? throw some GFO carbon end of story =D
Are you using a protein skimmer?
1: 40 Gallon Breeder , No Sump
2: 6 fishes in total,2 clown,1 fire Angel,1 coral Beauty ,1 fire goby and 1 Diamond goby.
3: non are grazzer
4nce a day, small cube of Mysis shrimp
5: Weekly tests
6: 6x turbo snails, 1 cleaner shrimp, 4 lasarus snails, 5 hermit crabs, 2 sand sifting starfish and a sea hare.
7: i started with the petco brand sea water then started mixing my own.
8: no sump or Refugion
9: N/A
10: No
11: 110% !
Ok. The only thing I can think of is that you have been mixing salt with tap water. That has to stop. You can buy a RO/DI unit or you can cart water like I do. Meaning I buy RO/DI water at .50 cents a gallon and transport 40 gallons a month from my LFS. Yes its a pain in the a>> but no floods or leaks or filters to change.
You do not have a skimmer or a sump or a refugium. This means you will have to do more regular water changes, more water movement with some surface water movement as well.
Also how many fish can you stock in a 40 gallon setup?
3gal to 1" of fish?
4gal to 1" of fish?
5gal to 1" of fish?
Let say 4 to 1 to make it easy so that's 10" of fish
gobies say (2) 2", angels (2) 4", clowns (2) 3" so you are ok there but only just.
Clean up crew is scant. Turbos only cruise rocks and glass, cleaner shrimp N/A, nasarus snails you need at least 10 more, Crabs you need diverse types and plenty of them 20 would be good as they eat different type of algae they also stir the very top of the sand (they die, get stuck and die, get eaten... and die) so more is better. Never had luck with sand sifting stars as I never have that much build up in the sand. Brittle stars are better as they cruise the sand and the rock work.
This is not a bible just a recommendation as I have not touched on a number of other things.
1) Power heads? how many? continuous or cycle?
2) filtration? Hang on back? canister?
3) water change schedule?
4) what are your current water readings?
Continue to syphon off the buildup and gently stir the sand weekly. Start a tank thread and you will get great tips and you will be able to post follow up photos showing progress!