Snails v. Crabs

[Dag]

Early on I made the decision to go with snails, rather than crabs, for reasons I've now mostly forgotten. Crabs are omnivores and eat everything, including snails and other critters in the DSB. Perhaps they disturb the DSB as well. Anyways, as you may remember, I've been experiencing about .1 nitrites and 1-3 nitrates, notwithstanding a DSB and a refugium. Anthony, what would you do, stick with a crabless, snail environment or add crabs? Other than the nitrites/nitrates traces, there does not appear to be an algae problem.

[Anthony Calfo]

I have had a long-standing opinion to not recommend/use crabs in reef tanks for most any reason. They really all are essentially problematic in time (unduly so at least - mainly the oppotunistic predator thing).

If you must use snails, please seek only cultured ones (or ones that reproduce easily in aquaria) like Cerithium, Trochus, Strombus from IPSF.com (tiny species), Stomatella, etc..

Do avoid wild caught Astraea or Turbo when there are more responsible options like those listed above.

Skim aggressively too/instead to temper nuisance algae :)

[Dag]

What about Nassarius snails? I thought they were among the best meat-eaters.

[Anthony Calfo]

it/they (good scavenger or not) is beside the point I'm trying to make: cultured or culturable species like the above listed versus wild caught and non-reproductive in aquaria (Nassarius e.g. at present).

[Meisen]

Anthony,

Not sure if you are reading this anymore but just to play devils advocate, arent snails somewhat of a "renewable" resource? Of all the animals we cause others to take out of the ocean for us, these snails seem to be on the rather prolific side. I know this argument has been used before with fisheries on species that were essentially though to be "infinite" but with a rather short life cycle, hundreds or even thousands of eggs released per individual, a very generalist herbivore feeding strategy and ability to make use of several different types of habitats (including but not only coral reefs)....dont Turbo, Ilynasaryia (spelling?), Nassarius and Astrea snails stand a better chance of providing a sustainable yield than most of the corals/reef fishes we keep?
Maybe the regulation is lacking to prevent things from getting worse but boy, I can't honestly imagine our rather small hobby depleting a whole ecosysten area of snails anytime soon. You certainly couldnt do it if you tried!!!!!

[Anthony Calfo]

On the contrary, my friend - numerous snails, reef hermits, cucumbers and other detritavore type reef inverts were/are collected in such staggeringly high numbers that some states/communities imposed (emergency in some cases as I recall) legislation to limit or reduce previously liberal or unregulated collections of said animals.

With Astraea, blue/red eg hermits for example... their sudden popularity when first introduced spiked collections from a few hundred per week to many thousands per day. A few collectors really abused this (taking excess of 5000 pieces per day!).

The survival rate foe their gametes is also comparatively low (common with heavy broadcast spawners... they are plankton/fodder).

And as stated above, I refer to the species like Nassarius or turbos (in contrast to Cerithium, Strombus, Stomatella) that do not reproduce successfully in captivity to any significant extent if at all.

To adopt the attitude that we can just take from a seemingly "limitless" resource, even if true, when their are better alternatives (self-sustaining species of reproducable culture) is not only unhealthy, but it is not the conduct of a conscientious aquarist.

Please do reconsider your position.

Anthony

[bwb007]

ANTHONY,i know you are a very busy person doing research and writing very informative books, i didn't quite understand your answer-are you saying that crabs are a good thing in a reef aquarium or are you saying they are bad?i am not asking for a recommendation just an interputation...thank you for taking the time to answer my question

[bwb007]

anthony,i do agree with you,there is nothing "limitess" in this world, that kind of thinking has caused reef systems all over the world to be in danger of disappearing or have already disappeared and when they are gone,they are gone forever-at least in our lifetime

[Anthony Calfo]

No worries, my friend... you must have glanced over my post above:

[I have had a long-standing opinion to not recommend/use crabs in reef tanks for most any reason. They really all are essentially problematic in time]

I have indeed had this position for a long time. Crabs are great scavengers for FO tanks without invertebrates or slow, small, weak fishes... but they are destructive and a net burden in reef tanks. Point blank: very few if any crabs are ultimately useful in reef aquariums IMO.

Most crabs are opportunistic predators. Just look at their claws - form follows function. Those claws are not ornaments :D

Many will ravage sand beds of other desirable life forms... they will catch and kill fishes when they can (sick, sleeping, injured fishes are at risk), etc. More thana few people have lost even medium/lg fishes to overgrown "Mithrax" (Mithraculus) crabs for example. So much for reef-safe ;)

Anthony

[bwb007]

anthony,thank you for your response to my question
best of luck to you in the future

[jklaw]

could the porcelan anemone crab be an exception to your rule. i have one in my bta and he never seems to leave it, he is also very small.

[Anthony Calfo]

jklaw,

indeed my friend... there are always exceptions. Few things in this world are so purely black or white.

as mentioned above, "form follows function". And your porcellain crab has modified feeding aspects - feather appendages which filter feed (harmless).

Anthony :)

[Meisen]

Anthony,

How could collection be that complete? Everywhere I have ever snorkeled, I have seen tens of thousands of snails, hermits, cukes, crabs, urchins etc. How could you collect any real % over hundreds of thousands of acres of flats in the USA and Carribean alone? We must be talking billions of astreas here....could the hobby support 2.5 billion dollars in astrea sales? Was the "emergency" legislation based on science or just "wow a lot of people are taking stuff out of the water"?

My point about some of these species being broadcast spawners was also that it would be rather easy to set aside areas where populations were unmolested (as has been done in many areas)...these would continually seed the collection areas. I am all for sustainable use here, just wondering if its silly to regulate species that are 1. plentiful 2. hard to find (cryptic, nocturnal or deep sand dwelling) and 3. easily replenished from protected areas. I would think that we should focus on shutting down the live coral trade first if we really want to have the biggest conservation impact...are there reasons why that thinking is erroneous?

Please dont take the tone here the wrong way, as I said I am posing questions I want your opinion (which I respect highly) on. I am hoping you have better answers than I do here. Thanks again for your time.

[Anthony Calfo]

There are species that (presently) fall under the fair assessment of "sustainable harvest" and there are those that clearly do not. Of course, there are others that fall in between (our snails perhaps) and we error on the conservative side for them usually (limiting collections). Of the many things that skew this valuation, the burden of a given fishery must be considered.

(Over)collecting a given population of urchins, snails or other algae grazers, for example, has a far greater negative impact on the reef than (over)collecting a comparative population size of say...waspfish, or damsels.

Speaking further more to sustainable harvest, there is the very real issue of rates of replacement. Organisms like snails with high volume spawns have staggeringly poor rates of successful fertilization. Adding overcollection, or disease (like with the Florida urchins) to the equation and things can go from plentiful to endangered in less than 10 years.

And beyond all this, you are still missing my point : if you are truly an empathetic/conscientious aquarist... why would you want to take from a wild source (limited, however vast it may seem right now) when there are better, captively reproducable species available instead? It makes no sense to me. Rather insensitive.

And not upsetting to me at all, but rather illuminating to me just how ignorant (respectfully, as in "not knowing") you are on the actual industry and science of the aquarium hobby, is your statement that [we should perhaps be looking at shutting down the coral trade instead]. I just don't know where to begin here... so much to say/enlighten you with. I regret that I do not have the personal time for it.

Let me suggest you visit our free content website wetwebmedia.com where we have enormous archives of information that include business and science data on the aquarium trade that will help you gain a better understanding for how things work.

Conside this though: go to a given patch of reef and collect all of the urchins, snails, anemones and staghorn acropora... then come back 6 and 12 months later and see who recovers. Only one will impress you (the staghorn corals... fast regrowth as if nothing happend)... some will concern you (urchins and snails remarkably slow to recover)... and one will be painfully sobering to you (many years later... still no anemones). Its all about sustainable harvest.

Best of luck in life to you... I'l get back to work trying to finish volume 2 of our NMA series for conscientious aquarists ;) I do hope you count yourself as one of them, my friend.

kindly,

Anthony

[Treeman]

Well said Anthony, but to defend some people here. It is very hard to know what you speak about when you are just a hobbiest. I had know idea how things really worked until I decided to become a grower. I know the info is out there but it is not something you can see or feel unless you know where to look...ie...wetwebmedia.com, reefs.org and such.

Keep up the great work!

Matt

[Anthony Calfo]

Thanks Matt/all for understanding. :)

And let me assure you too that I am really just a hobbyist in kind. Aside from professional experience as a merchant/grower, etc... I have no academic/fisheries work experience or university/lab affiliations, etc.

I simply read and travel about the business of aquatic science/hobby. Some of this understandably is not readily available to the majority of aquarists... not everybody has the time/money to fly to 2, 4 10 different conferences each year (for those that do, they run the gamut in focus depending on your interest... Interzoo in Nurnberg (global introductions to new hardware), Aquarama in Singapore (premiere livestock exposition), MACNA is one of the best here in the states for hobbyists, etc). Don't assume that you cannot afford to go to these events either... many are quite affordable and the lessons learned there are priceless. For example, I recently priced a coast to coast airfare for a friend to Boston MACNA (just over $200)... and recently was booking flights to Germany (Interzoo this May) for $278 from Pittsburgh. I strongly encourage aquarists that have the means to invest that $500 or so each year into their hobby/education/knowledge into at least one good conference each year.

If not, all of us can access (libraries, subscriptions and/or online) other pertinent data with little effort. Some folks will find industry news useful (seek Pet Business, Pet Age/Pet Supplies marketing magazines or a PIJAC (lobbyist) publications to get a pulse on the commerce side of our hobby). And begin with CITES, NOAH and the plethora of fisheries data (seek by state/country, etc) that abounds on the Internet.

This is such a broad topic that we cannot pin it down to even a few key reference points. Thankfully, there is so much information out there! How wonderful the Information Age is :D

The best advice I can give anybody that thirsts for more knowledge on just about anything, is... to take a class at a local university (community campus for example) on refining their Internet searching/surfing. It really is an art form to navigate the Web and get the most out of it (weeding out the advertising and drivel). That is a real key to hold... truly so :)

Explore, explore!

Anthony

[Treeman]

Hi Anthony,

I couldn't agree with you more! I took a class a couple of weeks ago at Harbor Branch Oceanic Institute (where ORA is) and it was amazing at the amount of information that they could throw at you. A couple days there I had brain hemmorages:D And I am going to IMAC and MACNA. Maybe I will try overseas at a later date.

I thought I had learned quite a bit until I started talking to the real people in the business, then you really start to learn.

PS. I got my copy of CORAL magazine last week. What a great read!! Can't wait for the next issue. Lots of info.

Matt

[Anthony Calfo]

So true my friend. :)

And Yes... Daniel Knop's magazine (Coral) is outstanding! For many years we (aquarists) have had to struggle with rough translations if you wanted to enjoy this work.

Very glad to see Leng Sy picking up the gauntlet and publishing it in English. We will all benefit greatly from it.

be chatting soon,

Anthony

[Meisen]

Anthony,

Thanks for the illuminating reply. I was interested in hearing what you think about these issues and it will help me when I get asked those same questions.

Dag, sorry if this seems like somewhat of a hijack.