DSB flow rate

[scotty333]

Guys
My nitrates are 75ppm and not coming down naturally
My sand is 6” deep and the baffle height is 12” so the flow over the top of the sand will be very low ( 525 ltr tank inc sump with 5000 ltr return
Question is should the flow be a bit more just over the surface by adding a small pump? Or is it that the 8 year old sand is expired?

 

[The_Paradox]

How long has it been set up this way? Is the sand 8 years old or is the sand bed 8 years old? What type of sand is it? If it’s basic silica sand it’s not expired. I’ve never had to reset a deep sand bed before but if you wanted to you can. Just be sure to shut off the return and isolate that chamber before removing the sand. Then rinse the chamber and sand and your reset to day 1.

 

[scotty333]

8 years everything is 8 years old inc the water
The sands from the beach in Portugal
So flow isn’t the issue?

 

[scotty333]

Also my display has a 3-4” bed (1/2 the floor ) with a steady flow over

 

[scotty333]

Introduced a small pump to flow over the top of the dsb