Diatom bloom puzzle

[golfgod3]

Ok been doing a lot of reading about diatoms. My big tank 90gal with 30gal sump has been fighting diatoms the last month! My 40 gallon with hob refugium hasn’t! Both use the same RODI water source with the same instant ocean reef crystal salt. I do monthly water changes, both have same lights and lighting cycle. I would think if I had silicates from my RODI water both tanks would have diatom bloom??? I have put a skimmer on big tank been running two weeks now with no noticeable improvement in outbreak. I am also running a mixed filter bag of gfo and carbon in each tank. Any ideas I am considering turning off lights for couple days to see if that breaks chain??? But I’d like to know cause?? Also want to note my water test show no nitrates, nitrites, phosphates, in either tank and the cheato I’ve tried in both dies due to I’m guessing from lack of nutrients.

Any ideas or thoughts would be greatly appreciated!!!

[fishbox]

Are you sure they're diatoms and not dino's? I believe others with the dino issues have reported getting them in one tank and not the other even though they shared the same sump.

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[golfgod3]

Almost positive they are diatom! Several people have identified them!

[mcgyvr]

Age of tank?
I'm really not surprised at all that a larger tank is having more of a diatom issue vs a smaller one.. More sand/more rock/more glass,etc... all can contribute some to a diatom bloom..

[eredder]

I had a heck of a time in my 90 with diatoms. I shortened the lighting schedule and it finally went away. I had them on way too long. It is my first saltwater tank.