Conflicting Advice

[AliRichardson]

I have read that the DSB is a great way to promote the growth of bacteria that will effectively convert nitrates into nitrogen in an oxygen starved environment.

I am happy with that statement however I have some questions...

1. How does this "cleaner" water flow back into the system efficiently when the flow in a DSB is extremely restricted. Is this poor flow a limitation to its effectiveness?

2. Many LFSs I have been to say that the DSB is a bad thing to have and that an inch of sand is the absolute max. The reason for this being that harmful toxins can be built up from bacteria and will gradually (and exponentially) pollute the system.

I can understand both of these theories but I want to know the truth I guess lol. We understandably took the advice of the LFS and we have very little sand. Some areas can get blown by a powerhead and in seconds expose glass.

Any knowledge you can pass on to me about the DSB would be great

 

[ValerieM]

Lots of people promoted the DSB idea and that's what I went with originally. Things went great until about a year later when all the junk that had built up in the sandbed started leaching back out and it was a nightmare of nitrates, phosphates, the resulting algae, couldn't keep my param's straight, and endless water changes.

Needless to say I have since gone BB and all my problems went away and never came back. I am definitely BB all the way now and all my future SW and reef tanks will be BB with a faux sand bed for the sand 'look'. There are more and more articles coming out now about how DSB are coming back to bite people in the behind after years of buildup has accumulated in the sandbed. Obviously tank size and sand sifters affect how quickly it will be before the inevitable crash. But not everyone is doomed for failure with a DSB. Changing out the sandbed every year or two helps, as does vacuuming...however the regular vacuuming by virtue of the fact that it stirs up the sandbed kind of defeats the purpose of a DSB.

I think the best choice is the SSB if you want sand/substrate since it is the easiest to take care of. The DSB can be done successfully but there are a lot of hidden dangers that you need to keep in mind.

 

[andywg]

Articles seem to show that most people who had catastrophic failure with DSB set them up wrong. The guide is to have either less than an inch or more than 6". Some people got all hung up over plenums and the like as well, though these have little effect unless your DSB is measured in multiples of feet and not inches.

They can work well if done correctly, but as mentioned above many people do them wrong.

The toxic gas build up is very unlikely. Hydrogen sulphate (very bad) can occur in a sand bed but the moment it comes into contact with oxygen it will react and change into something else. Our tanks are well oxygenated (unless your fish are gasping for "air" at the surface) so it will never form in a large enough bubble to cause any harm.

There are some fears about it becoming a sink for storing nutrients to let them back out. I have not read a great deal of scientific approaches to this, but rather a few accounts from aquarists.

Bare Bottom deals with the problem in a different way. Rather than having something to deal with the waste, it tries to have the waste removed before it can break down and is very effective for this, though you do tend to lose the ability of the sand for buffering the tank.

I myself am a fan of a smaller sand bed in the display and fitting a nice large DSB in a sump where I can make it nice and deep without any real worries.

 

[AliRichardson]

Nice reading.

Just to keep you up-to-date with the chemistry.

Hydrogen sulphate (HSO3) the nasty you described as sometimes being present in DSBs will be in equilibrium with water and dissolved oxygen to form the killer that is H2SO4 otherwise know as Sulphuric acid.

 

[SkiFletch]

I wholeheartedly agree with Andy. Also we as aquarists tend to mince words when talking about DSBs, making things even more confusing. When some people refer to a DSB they mean a deep sand bed inside the display tank. A thick layer of sand in the display itself is a nightmare under even the best of conditions longterm. You'll get lots of detritus settling in the sand bed and it will eventually loose its capacity to hold nutrients and begin leeching them back into the water column. As Andy mentioned, formation of harmful toxins in a sand bed in the display tank is very unlikely, but nutrient buildup due to detritus is a big problem.

An effective method for operating a "DSB" is the RDSB or remote deep sand bed. The use of a 5gal bucket filled almoast to the top with sand and a low flow over the top of it seems to be an excellent means of getting all the benefits of a DSB without all the hassles of a display tank version. You get the benefit of a fantastic hypoxic zone at the bottom of the sand bed to harbor bacteria to break down nitrate to N2, you dont have to worry about fish or inverts stirring up dangerous particles (if they even are created) and detritus won't settle and make it release nutrients back into the water. And if something goes wrong and you need to remove it... Just remove it. 5gal buckets are convenient for that purpose

 

[pleder]

I'd recommend the book Live sand Secrets by Dr. Bob Goeman. It's worth the read.

 

[Ehudd]

what does dsb mean

 

[AliRichardson]

what does dsb mean

Deep sand bed

 

[joseywhales]

I have about 2" of sand in my tank. My question is how often or do I need to remove the rock and vac under the rock to get the detrius out?

 

[SkiFletch]

Just try and vac around the foundation of your rocks, then every year or two its a good idea to re-set the tank and do a full cleaning