good crabs / bad crabs

[ToddinAtl]

Hi All,
I've got a 80 G tank setup for about 5 weeks now. 120+ #LR. Coralline is starting to grow in very small spots, however, I've put a couple rocks in that had button polyps / mushrooms on them. These rocks are (were) totally covered in purple coralline. The hermit crabs (app 30) seem to eat this like the chocolate coating on an icecream. I went to 3 different stores to purchase the crabs, so I have 3 different types (at least) red legs, blue legs, and some brown/white leg types. Is there a rule? Is this normal....I want the coralline more than the crabs, realizing they both have a function. Sorry if this is redundant but I couldn't find any other posts adressing this...Thanks, Todd

 

[2poor2reef]

I don't keep any hermits in my systems because they are omnivorous and will eat live animals. I'd rather have clean up crew that is either herbivorous or strictly carion eaters. Hermits are a bit too indescriminate for me. When I did keep hermits I noticed that they would eat corraline algae but it was primarily when it was loose such as when new rock was added. Any established tank your size with existing corraline spores and good calcium/alkalinity levels will grow coralline well in excess of what a couple of dozen hermits can eat in my opinion. I keep a royal tuxedo urchin that lives almost exclusively on coralline algae and he can't wipe out corraline in my 12g tank. So I wouldn't get rid of the hermits just because of that. For future clean up crew I would recommend non-hermits for similar roles such as nassarius snails for carion scavenging, queen conchs for diatom and hair algae control, cerith snails for film algae, spaghetti worms for detritus, etc.

[ October 29, 2001: Message edited by: 2poor2reef ]</p>

 

[Dragonlady]

IME, most hermit crabs seem to do more harm than good unless they are in your sump/refugium. They seem to eat almost anything. Scarlet hermit crabs are the safest hermit crab for a reef, but there is a look alike red species that grows quite large and destructive. IMO, snails do a much better job of controlling nuisance algae, but there is a good possibility that your existing hermits will kill snails and take over their shell. I have one scarlet hermit crab in my tank, and a blue legged hermit in my sump. The blue leg hermit was introduced by accident as a hitch hiker and wrecked havoc on a healthy colony of 3 year old corynactis polyps when I went on vacation. The corynactis are only now starting to show up again.

 

[Rich-n-poor]

I like hermits myself BUT.......

I believe there are some drawbacks to them such as the fact that they do eat coralline algea I read a good article on this but cant seem to find it since then

The red and blue legs I am familiar with but the other species you mentioned I have never seen. are they left handed hermits with one claw much larger than the other ? If not they may not be reef safe.

Hermits do best when they are kept in low numbers like 1 per 5 gallon water or less and I am leaning towards snails myself lately

They also must have grow out shells to change into when they grow. I have never seen a hermit attack a snail for a shell in my tank but I have always had grow out shells.

I like diversity so I say hermits are good but only in low numbers with plenty of shells

HTH

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Men's Health Forum

 

[Katspaw]

I would say stay away from the hermits. I started out with blue legged ones. They never eat my coraline algae but they kill my snails for there shells, I had made sure to place lots of empty shells in the tank for their growing too. They seemed to have missed the new homes and just enjoyed killing the snail population instead. I have slowly removed all of them to the refugium, but then again they started causing havoc down there too. So they were moved over to the sump. Only to clog the intake pump. So now they are happily in some one elses tank, I took them back to the LFS.

Problem solved. I only keep snails and worms as a clean up crew now.

Tracey

 

[BReefCase]

Hermits are one of the most beneficial and interesting inhabitants you can keep in a reef -- provided the reef keeper does his part.

I currently have "micro hermits" from IPSF, and both scarlet and black-and-white hermits from Premium Aquatics. All are currently reproducing in my tanks. I also have as many different kinds of snails as I can find in the reef hobby, and the hermits have never killed a single one that I am aware of, either for food or shells.

I've never had a single bad experience in many years of keeping all kinds of small reef hermits. The predation problems reefers report with hermits are due to too much population density, too little of the RIGHT food, and no SUITABLE grow-out shells (you need many extra shells per hermit, and of the kind and size that the hermit, not the reefer, views as suitable).

You can't expect hermits to both mow down massive amounts of unwanted green algae when the tank is new and blooming, and then eat NOTHING after the tank is mature and clean. That simplistic pet-store notion of the "cleanup crew" is one reef hobby needs to out grow and leave behind.

Animals need to eat every day. Hermits are active animals with high metabolisms. (I feed mine frozen Prime Reef with great success.) Starving hermits will eat whatever they can get to stay alive, and yes they will kill for shells because they will die without them.

But hermits will not normally kill living prey if suitable (again, suitable in the hermits view, not your view) food is available. It's a simple energy balance -- hermits won't kill food that runs away and struggles and fights back if easy dead food is available.

Reefers often see hermits attack dead animals or eat necrotic tissue off live ones and think the hermits are attacking rather than scavaging. Hermits will attack any dead matter in the reef, which is part of their value. I also keep Nassarius snails in my tanks for the same reason, but I wouldn't be without the hermits. You really are better off with both, as they fill slightly different niches.

Reefers who project complex human motivations like cruelty or malice onto the natural instinctive or survival actions of simple reef animals are just being thoughtless or ignorant. Hermits will behave predictably if you don't crowd them, don't starve them, and have LOTS of suitable empty shells for them.

If you want to keep hermits, treat them as reef specimens that are worth keeping in their own right. It's just a matter of providing for their few simple basic needs.

By the way -- by eating your coraline, the hermits are just spreading it around and helping it grow back even thicker -- another reason to keep them.

 

[Anonymous]

My scarlets are angels - love them. They are different from red legs though - scarlets have yellow eye stalks, red legs don't. I've heard that red legs are more agressive.

Blue legs are the devil. They have tons of grow out shells and killed off my snails for food. None of them wear the shells and they killed my nassarius snails which were much too small for homes.

 

[ToddinAtl]

Thanks everyone for your input. As usual it seems we are equally devided. As for the white / brown crabs, I have no idea if they are right or left handed (clawed). I'll try to get one to swing a baseball bat and report...kidding...thanks again