Troubles With Sandbed

[Sharkbait19]

Hello,
Apologies in advance for the long write-up, but I would like to provide as much background information as possible.

For the longest time, I have experienced troubles with my 40B reef tank, particularly with my corals, in which they would go from months with beautiful growth and happiness to suddenly dropping dead. The worst was a couple months ago when I had to catch my aggressive angelfish and moved some rocks and disturbed the sand, which caused the entire tank to go into shock, and many corals immediately melted away. The same happened last night, in which I had to shift a rock to remove an anemone, which kicked up a lot of debris. Knowing that doing so would cause a problem, I was much more proactive with water changes and moving my sensitive corals into quarantine. Nonetheless, the 40B became cloudy and even the hardiest corals look ticked off. The ones I moved into my other tank are already recovering though.

This has been the case time and time again, in which even the slightest disturbance of the sandbed causes catastrophe, sometimes able to be mitigated, other times worse. As of recent, it almost always causes major issues. What is most strange is that the parameters before and after the incident remained nearly the same (at least the ones that I would be regularly testing). In the past, I’d always pegged the coral deaths as a parameter issue, but whenever I had moved corals to the much less suitable quarantine environment, they’d immediately open up and even look better than they had before.

I decided to do some research as to what could be in my sandbed that, when kicked up, could cause such an issue, and that led me to learn all about hydrogen sulfide in deep sand beds. I do believe that this could be what gets kicked up and causes trouble, as my water always smells foul afterwards and there exist black and smelly patches underneath the top layer of sand. While I’d love to move forward by simply not disturbing the sandbed at all, I know this can be unrealistic, as even my sandsifting fish could cause a problem.

Is there a long term solution to this buildup of H2S, and is there possibly a way to neutralize it so that it does not remain a standing issue? Are there other sandbed-related issues with a tank that I am not accounting for?

As of right now, the parameters read:
Mag: 1395 ppm
Alk: 10.5 dKH
Nitrate: 7.5 ppm
pH: 7.9
PO4: 1 ppm
Calc: 430 ppm

The phosphate level is probably due to me using my well water (which is crazy high in phosphate levels) during last night's 50% water change, as I was more concerned about pulling the potential toxins out than raising the PO4 (the RO water takes hours to replenish), so I've put fresh phosguard in to lower those levels.

 

[The_Paradox]

Is you sand bed deep enough to go anaerobic?

 

[Sharkbait19]

It’s about 2.5 inches deep, possibly four at the deepest points.

 

[The_Paradox]

It’s about 3 inches deep, possibly four at the deepest points.

I guess to your question, does it need to be that deep? At 4” depending on your sands mesh you might be accumulating H2S.

 

[TangerineSpeedo]

What I do:
My sand is 1"- 1.5. I do not vacuum the sand when I do water changes, but when I do I will pick a corner to use a baster and stir up the sand. I also have CUC that stirs up the sand. Deep sand beds do have their purposes but they also have their drawbacks.

 

[Sharkbait19]

I guess to your question, does it need to be that deep? At 4” depending on your sands mesh you might be accumulating H2S.

It is variable across the tank - at the lowest it probably is about 2 inches.
It probably doesn’t need to be that deep, just always has been.
I do have a lot of nassarius snails, 2 conches, 2 pitho crabs, and a pistol shrimp all making a home in the sandbed.

 

[sgrosenb]

I'm not sure the best way to approach it, but if you're open to removing your sand, you may find that you have more success with the tank. I struggled with SPS for 2 years, at which point I removed my sand and added a filter roller and my tank is now shining. I like the look of the sand bed, but I was never able to keep my parameters in check with it, and I didn't like the maintenance of it. I know there are tons of people that have success with sand beds, but for me it was a game changer when I took it out.

 

[The_Paradox]

It is variable across the tank - at the lowest it probably is about 2 inches.
It probably doesn’t need to be that deep, just always has been.
I do have a lot of nassarius snails, 2 conches, 2 pitho crabs, and a pistol shrimp all making a home in the sandbed.

Based on that livestock I would knock it down to 1-3”.

 

[Sharkbait19]

I’m currently considering a hard reset on the tank in which I go bare bottom instead, but would like to ask your opinion first, @Randy Holmes-Farley. Is there a chemical additive, to your knowledge, that helps break down or neutralize H2S, and if so, how might I dose this?

 

[Lavey29]

My sand is 2 8nches deep. I turkey baste up a dust cloud weekly with no issues.

 

[flashsmith]

I stir my sand beds every other day
Turkey baste the rocks and scrape the glass with no issues. Constantly replenishing clean up crews can get expensive when you have bigger tanks. So I just do it myself. The urchins and fighting conchs do the rest.

 

[The_Paradox]

I’m currently considering a hard reset on the tank in which I go bare bottom instead, but would like to ask your opinion first, @Randy Holmes-Farley. Is there a chemical additive, to your knowledge, that helps break down or neutralize H2S, and if so, how might I dose this?

Sodium bicarb will do it but it’s not going to matter if it’s forming in an anaerobic environment and being released when you disturb pockets.

 

[basshead808]

I wish I had gone bare bottom

 

[The_Paradox]

I wish I had gone bare bottom

Just vacuum it out if you don’t want a substrate.

 

[Sharkbait19]

So I think I might remove the sand, but the issue is I own a pistol shrimp and goby that spend most of their time burrowing. Should I leave a thin layer of sand for them, or would I just be setting the tank up for the same catastrophe?

 

[Miami Reef]

So I think I might remove the sand, but the issue is I own a pistol shrimp and goby that spend most of their time burrowing. Should I leave a thin layer of sand for them, or would I just be setting the tank up for the same catastrophe?

You can leave a thin layer. Many people stir their shallow sand layer without issues.

 

[Sharkbait19]

In even a 1” sand layer, is H2S still a possible issue? Should I still clean it every week? Also, when changing from a deep sand bed to a thin one, would I be able to get away with just taking away some of the existing sand, or should I remove it all and start from scratch?

 

[The_Paradox]

In even a 1” sand layer, is H2S still a possible issue? Should I still clean it every week? Also, when changing from a deep sand bed to a thin one, would I be able to get away with just taking away some of the existing sand, or should I remove it all and start from scratch?

Possible in the same way you might get mauled by a Grizzly Bear while cleaning the tank. As long as it’s not a clay rich substrate any common mesh sand will be good up to 2-3”. As for how to thin it out, I would vacuum it and just do a water change after.

 

[Sharkbait19]

How does this plan sound—
1. Pull all livestock, rocks, etc. and put them in sterlite bins and empty quarantine tanks for a few hours
2. Heavily siphon the sandbed and take out about 50%, so it’s about an even 1 inch across the tank
3. Leave any areas underneath large rocks bare bottom, and line that area with egg crate to provide some space between the rocks and the glass bottom (I’m rather paranoid about placing the rocks directly on the floor)
4. Run some carbon and a few hours later, put the fish and less sensitive corals back.
5. Over the next few days, acclimate in some of the more sensitive corals.

Moving forward, are there any good 40B fish or inverts that really excel at sand sifting, specifically doing so between the rocks and the glass bottom? My pistol shrimp has always done a great job with the right side of the tank, but the area underneath the large rock on the left side is never disturbed by anything.