Removing the black in the sand.
 

My 15g addon has about a 2 inch sand bed in it. The sand i can see in the front has gotten a big black patch in it.

right now the tank is almost empty on a lights off regiem. I tried using 4 24 inch cool white shop lights to just use it as a fuge with LR and the algaee went crazy. its in that time the black showed up as well.

There is also some black in the small dsb part of my sump although i think i will just remove that when i modify my sump in the near future. just leaving that chamber empty or putting more LR in there instead.

if i put a few more sand snails in there will the black slowly go away or will the snails avoid the black area?


should i just remove the sand?


would that sand be ok after a good washing to make frag plugs out of?

I would remove the sand in that area, rinse it with old tank water, then add back to your tank once dry, add it back in thin layers and you should be good.
Get a sandsifting goby like the diamond goby or a yellow head.

it is because the sand is settling and now is compacting and killing the beneficial stuff if there is only just a small spot you can vacuum the sand and put new water to top the tank up. Vacuum every 3 weeks and it will be OK you just need to get the dead stuff out of there. A sand sifting Gobi will control this in the future. If the area is large you may want to vacuum and them take it out and rinse it and place it back in the tank.

Bill