Originally Posted by Lshann14
I'm not new to this at all, but I have done everything that I can think of right this second to fix my problem and nothing has helped.
Just to start guiding you in the right direction, if you aren't new at saltwater at all then why are you under the belief that diatoms are caused by phosphates? Diatoms feed on silicates, which can be found in our sand and rock but is normally consumed in the early life of a tank, unless there is a large disturbance of the sandbed allowing unconsumed silicates to be exposed and able to be consumed.
As you earlier stated the tank has been set up for 6 years, there is a chance that something disturbing a 6 year old sandbed can cause a diatom bloom...but it can also cause a nutrient spike in the system since all kinds of uneaten food and poop can build up along the rocks and in the sand. This can cause algae, dinos, and cyano
blooms...from minor to major. It is much more likely that you are experiencing this. This is even something that occurs 'often' in tanks around this age and goes unaddressed as what is causing it goes unidentified...so much it has been coined 'old tank syndrome'.
As it appears you are using one of the red max tank setups, I'd suggest cleaning out as much of things as you can with the sump, skimmer, sponges...so on. Is the skimmer stock? If so I haven't heard much positive about them and maybe an upgrade to a more quality skimmer would help as well. During your next water change you may want to see if you can siphon out any build up around rocks that you can see along with lightly over the issue you are trying to describe.