Old DSB remnants: To re-DSB, SSB, or nada.

[garcastle2]

I had a 7" deep sand bed in my 90ga for a few years. Then out of fear of buildup and a desire to get more space for the fish, I took about the bulk of the ~300 lbs of carribean play sand that was well, rippened over time.

Every once in a while when I do a water change I will suck out a bit more sand. I can't say I'm a fan of the idea of the rock being on the bottom glass with no cushion whatsoever but maybe I'm being silly.

I just tore out every bit of macro algae I could get a hold of and sucked out another 10-15 lbs of ancient sand which did not stink nearly as bad as it had when I tore out the DSB.

My question is: what can really build up in old sand? Should I try to get all of it out and then maybe toss in a washed fresh 50-lb bag to have a shallow bed? Is it wise to clear it all out every couple years? I remember reading years ago about hydrogen sulfide(?) buildup?

My phosphate level sucks which I am finally actively working on:
Replaced a leaky Black Fin with a Hammerhead.
Added two powerheads (finally!) and may upgrade them to MP40s.
Have been doing a 4-5% water change each night for 2 weeks.
Did a 10% water change today and may do another 10%.

My toddler and infant both love the tank as does about every other kid that comes in our house so it's time to raise the bar. :^)

Thank you for any input! (yes I live in the NE where I can get the occasional Home Depot good "play" sand)

[bertoni]

I ran two DSB tanks for about 10 years each, and nothing built up in the in sand, as far as I could tell. There will be some hydrogen sulfide in your sand, but not necessarily enough to be a problem. Mine never was.

That said, higher nutrient levels can cause phosphate to adsorb onto the sand. As you drop the phosphate level in the water column, that phosphate will leach out, slowing the drop in phosphate. If you're concerned, you could remove the sand. It's safe and easy to do.