DSB: Different approaches?

[Mark Cooper]

I have been reading about deep sand beds on reefcentral, wetwebmedia, and
have googled articles from this group and the web.


Here is what I have distilled from these references:

- it is the creatures in the sand that are most important, not what type
of sand.

- you don't have to use calcerous sands, silica will work just as well,
and are much cheaper.

- you need at least 4 inches depth to see the benefits of a DSB. (Shimek
and Fenner both say this).

- the bags of "live" sand at the LFS are next to useless, and you're
better off getting a live sand booster from someone like IndoPacific .

- a shallower bed will still have beneficial bacteria, but for full de-
nitrification you need a deeper bed.


I know that YMMV is the law of the land with the fishkeeping hobby, but
I'd like to hear opinions/experiences on the above.


Thanks,
Mark

[Tidepool Geek]

"Mark Cooper" > wrote in message

> I'd like to hear opinions/experiences on the above.
>

Hi Mark,

You might find the following two part article from Advanced Aquarist Online
Magazine to be of interest:
http://www.advancedaquarist.com/2005/6/aafeature (part 1)
http://www.advancedaquarist.com/2005/7/aafeature (part 2)

The short version is that Toonen & Wee found the following:

1. That there is very little difference in the denitrification abilities of
various types of sand beds.

2. That shallow sand beds seem to be somewhat better able to process
phosphate.

3. That fine sediments are much better at processing phosphate.

4. That there is a small but significant improvement in animal mortality
associated with deep beds.

I think that it's important to keep in mind that these experiments were
intended to document only the water processing abilities of various types of
sandbeds. Further, the tests were done over a short period of time and with
a very restricted group of animals. I mention this, not to cast aspersions
on Toonen & Wee's very valuable experiment, but to point out that it doesn't
address many of the arguments in favor of deep beds that you would find in
Ron Shimek's articles.

As I see it, the trade-off is one of aesthetics versus utility. Many people
might find a 4 inch layer of sand to be interesting to look at but very few
would find such a thing attractive. OTOH: Depending on what sort of display
animals you have and on how much management you are willing to do, a deep
bed can, in and of itself, address some things that would otherwise be left
to the aquarist. Further, most of these management issues would be handled
better by the (presumed) complexity of a deep bed.

My own interest is in keeping cold water animals that are native to my area.
For that application, a deep bed is just about mandatory since a very high
proportion of the animals to be shown are filter-feeders that will depend,
to varying degrees, on the microfauna produced by the bed. Further, a goodly
number of our animals (including three species of really pretty anemones)
prefer to be partially buried in sand and some of the most effective
scavengers like to spend their 'down time' buried in sand.

I'm sure that you'll get a wide variety of responses to your post and that
many of them will directly conflict with each other. The thing to remember
is that every aquarium is different in a bewildering number of ways and
that, as such, every aquarium has different needs in terms of management.
Some mixes of animals will make a deep bed virtually mandatory but in many
cases an aquarium with the proper mix of animals will do fine with a shallow
sand bed of whatever degree of coarseness/fineness is convenient.

My personal opinion (and it's only an opinion) is that you can't go wrong
with a deep bed as described by Shimek. You may not absolutely need such a
bed but, like the chicken soup argument, 'It couldn't hurt!' OTOH: If you go
with a shallow bed there may be animals that either don't do well or that
require more effort on your part than you can afford to give. I think SPS
corals are an example of this but, as mentioned above, I'm a cold water guy
so I could very well be wrong.


Sedimentally yours,

TPG

[Rocco Moretti]

Tidepool Geek wrote:
> "Mark Cooper" > wrote in message
>
>
>>I'd like to hear opinions/experiences on the above.
>>
>
>
> Hi Mark,
>
> You might find the following two part article from Advanced Aquarist Online
> Magazine to be of interest:
> http://www.advancedaquarist.com/2005/6/aafeature (part 1)
> http://www.advancedaquarist.com/2005/7/aafeature (part 2)
>
> The short version is that Toonen & Wee found the following:

> 3. That fine sediments are much better at processing phosphate.

But you must remember the caveat from part one - the coarse and fine
sediments were not from the same source, so differences in phosphate
levels might be due to the makeup of the substrate itself, rather than
any nutrient processing differences of coarse/fine.

> 4. That there is a small but significant improvement in animal mortality
> associated with deep beds.

I'm a little disappointed by their analysis. In their mortality studies
they counted all of the deaths as equal, that is, 1 Puffer = 1 Urchin =
1 hermit = 1 snail.

All deaths are regretable, but from a hobbist's perspective, there is a
difference between loosing your $50 centerpiece puffer and one of your
4/$12 cleanup crew. At the very least, the fish/invertibrate sensitivity
difference should be considered.

> My personal opinion (and it's only an opinion) is that you can't go wrong
> with a deep bed as described by Shimek. You may not absolutely need such a
> bed but, like the chicken soup argument, 'It couldn't hurt!' OTOH: If you go
> with a shallow bed there may be animals that either don't do well or that
> require more effort on your part than you can afford to give. I think SPS
> corals are an example of this but, as mentioned above, I'm a cold water guy
> so I could very well be wrong.

I'll just add, from the article:

"The basic conclusion from [Julian Sprung's] work (covered in more
detail in Delbeek, Sprung, In press) is that the location and volume of
rock as well as the surface shape of the sand or gravel (e.g., mounds,
sloped, or flat) can dramatically affect the efficiency of water flow,
oxygen diffusion and nutrient processing in the sandbed."

and

"So what does explain the differences among aquaria in these
experiments? Well, it turns out that the best predictor of aquarium
nutrient levels is quite simply the bioload and any animal deaths in the
tanks. Aquaria that had low (even undetectable) levels of ammonia,
nitrite and nitrate would suddenly show a substantial peak in
nitrogenous wastes following the death of an animal in the aquarium
(Fig. 11). Our results suggest that stocking level of the aquarium, and
any animal deaths, have a much greater effect on the overall water
quality than the specific design of the aquarium set-up you chose to
follow."

[Tidepool Geek]

Hi Rocco,

You make some very good points. If I may, I'd like to append a couple more
thoughts of my own to the discussion:

"Rocco Moretti" > wrote in message
...
>> The short version is that Toonen & Wee found the following:
>
>> 3. That fine sediments are much better at processing phosphate.
>
> But you must remember the caveat from part one - the coarse and fine
> sediments were not from the same source, so differences in phosphate
> levels might be due to the makeup of the substrate itself, rather than any
> nutrient processing differences of coarse/fine.
>
This is especially pertinent in light of the recent thread about the way in
which the 'phosphate sponge' type products work. My feeling is that this is
a gray area of T&W's findings that we're just going to have to live with.
The nature of ocean sediments and their deposition is such that it's
virtually impossible to get fine and coarse sediments from the same source.
Further, even if you can get coarse and fine from the same or adjoining
geographic area(s) the ocean will most likely have sorted them by density
which, by extension, means that they will be sorted by composition. Probably
the best way to minimize that variable would be to collect a wide variety of
sediments, assay them for their chemistry, and try to use the most similar
(chemically) sediments in both coarse and fine varieties for the experiment.
I suspect that going to those lengths was well beyond the time and financial
resources available.

>> 4. That there is a small but significant improvement in animal mortality
>> associated with deep beds.
>
> I'm a little disappointed by their analysis. In their mortality studies
> they counted all of the deaths as equal, that is, 1 Puffer = 1 Urchin = 1
> hermit = 1 snail.
>
Another good point, but I think it's arguable that the goals of the
experiment were best served by simplifying the mortality statistics. I do
agree that the mortality stats would have been more useful with the
following addenda:

1. Mortality by weight - obviously, a puffer is a bigger animal than a
hermit. Putting aside the dollar value it would still seem worthwhile to
track how each system did with respect to keeping its total biomass alive.
2. Mortality of vertebrates versus invertebrates - I'm not sure if this is
absolutely true but the 'conventional wisdom' is that inverts are usually
more sensitive to water quality problems. OTOH: I got the impression that
some of the inverts selected were intertidal animals that might be expected
to be more robust.

>
> "The basic conclusion from [Julian Sprung's] work (covered in more detail
> in Delbeek, Sprung, In press) is that the location and volume of rock as
> well as the surface shape of the sand or gravel (e.g., mounds, sloped, or
> flat) can dramatically affect the efficiency of water flow, oxygen
> diffusion and nutrient processing in the sandbed."
>
> and
>
> "So what does explain the differences among aquaria in these experiments?
> Well, it turns out that the best predictor of aquarium nutrient levels is
> quite simply the bioload and any animal deaths in the tanks.

I think that the value of T&W's experiment is that it helps give some
insight into why a given system works or why certain problems might arise. I
don't think it was their intent to determine what system is the best. Such a
determination is probably impossible given the variety of goals in
establishing an aquarium. If you were to list the 'perfect' components of
several types of aquaria (fish only, cephalopod, SPS reef, seahorse, etc.)
and showed them to someone with no foreknowledge (a Martian?) that person
might not even recognize that each was intended to simulate an ocean
environment.

Of course, T&W's experiment could have been more complete. They could have
used bigger tanks, a broader variety of animals, and, perhaps most
important, a much longer time frame. Unfortunately, such an expanded test
would have required several orders of magnitude more resources. Given the
constraints they had to work under this was a very valuable exercise.

The aquarium hobby is fortunate to have such people as Toonen, Wee, Delbeek,
Sprung, Shimek and others who are, not only dedicated hobbyists, but also
people trained in the scientific method. Taken alone, T&W's work is
interesting and useful but I think its true value can only be realized by
thinking of it as a building block to be used in conjunction with the work
of the other experts in the field.


Pontificationally yours,

TPG