Terrible Advice Tuesdays (T.A.Tues): More Hermits, Less Fish?
Terrible advice Tuesdays: Hermit crabs add to your bioload. Therefore, you should limit the number of hermit crabs you have in your tank so you can have more fish.
The rest of the story: Hermit crabs likely add some (emphasis on some) amount to the bioload to your tank as they do produce some waste. However, the amount of waste hermit crabs produce is small…very, very small. Therefore, don’t worry about the bioload from hermit crabs reducing the number of fish you can keep in your tank.
Browse the Store! Questions?
Cool tip just started 125 reef
Thanks for the tip Mark! I recently visited a lfs (not my lfs) to purchase a few hermit crabs and the sales person said they don’t carry them. He mentioned they only recommend adding snails and shrimp to all tanks since they are the only type of cleanup crew any fish tank really needs. I was in a rush and thought he was a little batty so I didn’t have time for a lengthy discussion but any advice on that?
Thanks
Devin
this helped me some. i am actually hoping to start a 50 gallon FOWLR and was wondering about this, lol. i was amazed by how many hermits some people have in their tanks.
thanks,
Quinn
@Devin. Not to steal mark’s thunder but the addition of hermit crabs adds to the diversity of your cleanup crew. They will scavenge anything they find on the rocks/sanded of your aquarium ranging from algae to detritus to any dead organism really… I find they are an indispensable part of my aquarium plus they are also interesting little critters to watch.
Some can be rather pretty too, especially the red and blue leg hermits. So long story short, I say add them!
80+ in our 450g
Oops, I meant sand bed*
Got at least a couple of dozen knocking around … plus a large bucket of random shells for them … they’re always busy working … make me smile even today … cheap as well so always a must for me 🙂
Unless you’re adding food to the tank specifically to feed your hermits, and with the exception of oxygen consumption and CO2 production, they are actually a net-negative bioload as they are detrivores consuming nutrients that are otherwise freely available as waste or are present because of waste (such as algae, diatoms, etc.) and are locking these nutrients up in their tissues.
@Josh…Thanks for the info, I have a few in my tank and agree they are great to watch scurry along the sand but was just baffled at why he would say such a thing. Wasn’t sure if I should stop including them all together or what, but thanks again!
I am about to start stocking my first reef tank. I recently saw/read somewhere they are bad and will knock your
corals/frags off the rock. True or false
Sean…anything (including fish) can knock an unattached coral/frag off a rock. A touch of superglue to give your frag a little holding power is the answer.
The benefit crabs give to your tank far outweighs the issue of an knocked over coral/frag that isn’t attached properly
I am a reef junkie and as to some people worry about this I don’t know that you could ever have to big of a clean up crew I personally have 30 or so hermit crabs in my 40 breeder of diffrent species along with lots of snails and shrimps and some odds and inns
I just added some hermit crabs to my FOWLR tank. They are doing an amzing job at keeping the tank clean. I’ve had fish for years and never thought about adding crabs to my tank. My LFS finally convinced me to do it. Glad I did
hermits are cool but it seems like all they do is fight each other and kill appropriate sized snails for their shells or just for the fun of it. there are plenty of shells (empty) in the tank for them to change. They also can climb over corals and cause them to freak out or possibly damage them by scratching their soft skins.(had a brain coral that does’nt like them using him as a doormat). Since, I have cut the number of hermits down and have added more snails and a few more conch’s.
Here is one that a lot of people heard..
“Red Legs or Blue Legs” Crabs ?
Which one is recommended and why?
Which one is not recommended and why?
Mark,
Great idea to have these “Terrible Advice Tuesdays (TOT)”, but why “TOT”? There is no “O” anywhere in there?
Also, please don’t use “TAT” as here in the UK “tat” means “cheap rubbish” – not the image you want at all!
Aside from this, please keep up the great work.
Cheap tat indeed … 😀 Although the advice is priceless … 😉
Red legs … seem to do best here … less evil all round … they’re the chilled out hermits from ours and many other folks experience … Scarlet Reef Hermits when available seem to be the best… 🙂
They might add some bioload but they also keep the rock/gravel clean from left over food. Therefore they will almost clean up the amount of bioload they add to the tank.
Nope. Crabs ARE biology additions– no question about it! IF you limit the definition to ‘producers of inorganic ammonia’ you are correct. But I like to look at the big picture of things-
our tanks are closed systems– over time, some ‘things’ build up and some ‘things’ are used up. crabs both add/give off to the pollution levels from their metabolism ( ammonia, DOCs etc) and take things out of the water for their metabolisms ( mineral and micro nutrient, molting needed etc).
I think its important to embrace the idea that anything living adds to load. Take nitrifying bacteria- it converts ammonia to nitrIte and then another tag team member converts nitrItes to NitrAtes. Over time, the build up of nitrAte becomes unbearable. Algae takes from the system and stored luxury nutrient. over time, it dies and leached all back into the system. Life is life and Life adds to the pollution in the tank. It really is only a function fo definition and how closely you count the details. JasPR
you can have too many if they eat your fish I suppose?!
I actually just recently received this advice! I wanted to increase my number of hermits because I noticed one of my rocks started sprouting more hair algae. I have nutrients under control now, but it’s the short hair algae that I can’t pick off easily…so I was thinking some hermits could munch on it. Someone told me “No! You can either get them or a watchman goby because of bioload.” I guess now I will get a couple more hermits and continue on with my fish plan, lol.
Vughn…hermit crabs are opportunistic feeders. If a fish is dead, they’ll eat it. IF a fish is dying, then might start picking at it. If a fish is healthy, then they won’t eat it. Even if they tried to grab a healthy fish, the fish would get away.
Karen…I certainly wouldn’t put a couple of hermits on par with the bioload of a watchman goby so I’d keep doing what you are doing – add the fish and the hermits
Mark,
Is there a rule of thumb for the amount of hermits in a tank? Like 1 per 1-2-3 gallons, etc? I have about 20 in my 75g with corals and fish along with 2 in my refugium. But I also have about 15 snails of varying sorts. Too enjoyable having the diversity of different types of each.
I’m sure there’s a “balance” where you can have too many, which is what Jaspr might be eluding too, but just curious what your magic number is, if you have one. Thanks.
I am not 100% certain that fish would be that much different. All animals in the tank can only eat and “process” what is added to the tank. I think that if you had a tank with only hermits and had a sufficient number to eat all the food that we normally feed our existing fish, you would end up with the same amount of waste and therefore the same bioload.
Just curious – can they ever get too big? It seems like I had one that got too big, I thought, for my tank – started being more opportunistic than I wanted; luckily I was able to return him.
Well mark I’m back started getting overwhelmed with alot of the different opinions of what to do or not to do it got confusing but I couldn’t give it up but my question is what is your friends web site that has cleanup crews I remember you had a link awhile back. Also thanks for
The website it’s a great place for info for newbies like me
Mark PLEASE!!! Talk about Aiptasia in a future episode. How to prevent it and what do now that you have it. Love your show thanks.
Speedy I use Kalkwasser, mix it with RO water to a watery paste and apply directly to Aiptasia with Turkey Baser, it kills them dead!!
Mark,
Is there good crabs and bad crabs to stay away from?
Thanks Ted. Yeh I have been using lemon juice it’s killing them but Im finding that its a losing battle with Aiptasia under rocks and hard to reach places. Its a 2.5yr old reef tank with no problems till now. No idea where they came from I have only added one urchin and one BTA in the past 3months. I have had enough and I think I might just buy a bunch of berghia nudibranches ASAP.
I have a 10 gallons aquarium with a 10 gallos sump I prepare everything my selfs, was fund and cheep. The thing is that I can’t have anemones or corals because they die. Lights 3 bulbs 50/50 coralife 20 watts each, 1 protein skimmer resun SK-300, 2 power head. What shout I do. I even use vodka. Fluval phosphate remover this did not work. I’m seekin wisdom from higher that means you Mark Callahan. Thanks
Hey Mark, I know this is not related to this topic but I was just wondering what type of sand you used on your 235 gallon build. Also do you siphon the sand? If so, how often? Keep up the good work! Thanks!
speedy
ive tried the berghias and didnt see results. they may have died before
they had a chance. i dont know!
sothe next thing i tried was an aptasia eating filefish! in about 2 weeks all my aptasia were gone!
it was very easy to catch so i let my friend borrow him to eat all his aptasia! worked great but i dont know if it would have started to eat my zoos after all the aptasia were gone since i took him out
I had an aptasia eating filefish in my tank almost from the start of it. He didn’t eat aptasia (or my corals), he died from something and after that I replaced him. The replacement wasn’t eating the aptasia, he was eating my fire n’ ice polyps, acan, christmas coral, and nibbling my blue tux sea urchin’s tentacles.
I tried replacing him and replacement #2 ended up nibbling only on my acan and christmas, along with the urchin and thus returned. I have two aptasia eating shrimp, but they don’t do much that I can tell. I just have one of those tanks full of odd fish.
I had hermits in my tank and they kept killing my snails. I had read that they do that to get the shells but they kept killing the others even after getting the larger shells. I took the hermits out that I had in the aquarium. Not sure what kind they were. I have read about other people having the same issue. What kind of hermit would be ok to have and would not kill all my snails. Do they bother corals at all? I also had shells everywhere and they were still killing the snails.
Thanks for the help and enjoy learning from the site.
wonderful post, thank you. http://youtu.be/ihnPPo6gqWo