DSB Removal

[dling]

I have a deep sand bed in my sump. Its been there for years. Ive been thinking about getting rid of it and replacing it with biofilter blocks. Im worried that it may cause my tank harm doing this. Also the bio blocks will be one sitting on top of the other and neither of them will have water flowing through them.The water will be flowing over the top surface of the of the top block only. Is this advisable ? or leave it alone ?

 

[Privateye]

The only concern that comes to my mind would be hydrogen sulfide, but it would have to be pretty concentrated to cause issues. If you start hitting some smelly, black sand then I'd perhaps slow down or do the process in parts. It depends how far in you are though. If you're 3/4 of the way done before you notice signs then you're probably fine to finish. Your nose will detect it at concentrations far lower than when it becomes a toxicity issue. It builds up from bacteria when you have anoxic zones without nitrate to process.

I also wouldn't worry about the blocks, but perhaps I'd have some slight separation (maybe 1 cm, give or take) between them for some water exchange. The more flow (i.e. oxygen) they receive the more nitrification they will perform. Less flow would promote more denitrification. They still need good access to nitrate to be effective at that though.

 

[exnisstech]

Maybe syphon it out a section at a time? I removed a 4-5" sand bed from a 180g DT before doing that with no issues.
What bio blocks are you going to use? I stacked some marine pure blocks in a sump once and they crumbled into a dirty pile.

 

[dling]

Maybe syphon it out a section at a time? I removed a 4-5" sand bed from a 180g DT before doing that with no issues.
What bio blocks are you going to use? I stacked some marine pure blocks in a sump once and they crumbled into a dirty pile.

Im looking at the

MARINEPURE Cermedia Aquarium Biofilter Media Block​

 

[dling]

They look like there maybe 8x8 wide 3or 4 inches deep or thick.

 

[fishface NJ]

I had Marinepure media blocks in my previous sump. It had been in there for about 4 years. When I went to upgrade my aquarium/sump setup, I went to grab the bricks in the sump and it was like wet paper/sand. It just crumbled