After 3 years, nitrates have crept in... DSB?

[shlap]

Hey guys, after having 0 nitrates for years, for the last 2 months I'm holding pretty steady at 20. I've tried water changes and Vodka dosing but nothing seems to work to bring them down. I suspect the cause is a DSB that formed/accumulated on one side of the tank. Originally I had about 2" sand throughout the tank but the undertow built it up on one side and I thought it looked cool so never intervened. To make matters worse my pistol shrimp has been going crazy digging through it lately.

So, two questions. First, can I safely remove the DSB a bit at a time? If so what is the process I should use aka how much can I remove at a time and how long should I wait between syphons?

Second, I've been Vodka dosing now for about 4 weeks and the only change I've noticed is a build up of brown slime in high flow areas that resembles cyno or dynos. There are tiny bubbles in it. :-( Its even started growing on some SPS and I'm afraid its going to kill them. For my 150gal tank I started at .7ml/day and have been increasing by .5ml each week. Should I stop the Vodka dosing or keep with it?

Any feedback much appreciated!

 

[bertoni]

The DSB likely can be removed at any time. There are two issues: it might be providing filtration, and disturbing it sometimes is an issue.

I'd probably siphon it out, and have some water on hand for changes, and add some fresh carbon, too. If the sandbed releases a lot of hydrogen sulfide, that can be toxic. You'll notice the odor, most likely.

If the DSB is doing a lot of filtration, which I doubt, the tank might see some ammonia for a bit. I'd have some Amquel or Prime on hand, just in case, and check the ammonia level now and then. Maybe right after removing the sandbed, hour hours later, and then maybe at the end of each day. That's probably overkill, but I tend to be the cautious type.

 

[shlap]

Thanks bertoni. Have any advice on the Vodka dosing? Should I stop? It seems I may be feeding the wrong kind of bacteria

 

[bertoni]

Hmm, I'd be tempted to stop the vodka for a bit. That might help or hurt. People report both effects. Sigh!