Questions regarding Mantis Shrimp Care

[Titangilas]

Hello!

have kept freshwater fish and reptiles for several years and the prospect of saltwater was always interesting but very daunting to me, but I recently got a great deal on a 90-gallon tank and felt the time was right to attempt to get into the hobby. When figuring out what to stock the tank with I found most of the fish that interested me either grew too large at adult size, or had very specific feeding requirements (mandarins, pipefish, shrimpfish etc). The one saltwater animal I have always loved that seemed like a decent choice for a first foray into saltwater was the Mantis Shrimp, and my local fish stores have them in semi-regularly. I had a number of questions about them as while there is a lot of good information out there some things conflict.

#1. It seems to be common practice to provide PVC burrows to give mantis shrimp the ability to molt in safety and darkness. My original plan given the size of a 90 for a mantis was to build a network of tunnels with pvc, like something you might see at the zoo for naked mole rats. However, a number of sources suggest that too many entrances might stress out the mantis or prevent it from molting. If this is the case, could multiple distinct, unconnected burrows be added and used by the mantis? Or would it just pick one and ignore all the others?

#2. Do the burrows need to be flat, or if a burrow started near the 'top' of the tank and worked down to the bottom, would that be sufficient? I had mused that as long as the mantis had at least one 'flat' burrow, the presence of a vertical burrow might incentivize it to explore the higher reaches of the aquarium instead of always sticking to the bottom.

#3. What is the ideal level of flow / suggested powerhead(s) for a tank of this size for this animal? I have heard from some sources that having strong flow is ideal for water quality, but others state that low flow is required because a strong flow will stress the shrimp and keep it hiding all day.

#4. There seems to be general consensus that 'strong' lighting leads to shell rot, but what is the appropriate lighting threshold? Usually when I see this described a blanket 'strong' is used rather than a given number that could be used to purchase an appropriate light.

#5. This is by far my most out there thought and I completely understand if this premise is ridiculous but I wanted some input from those far more educated on the subject. Given the great size of the tank for a mantis, and relative inability to share space with tank mates, would it be in any way reasonable to divide the tank in such a way that the mantis has access only to the bottom half of the tank, and fish or some other animals have access only to the top half? I imagine that using panes of acrylic or plexiglass a sort of 'second lid' could be placed in, but I can see a number of issues. Keeping the second lid clean, keeping the mantis from constantly trying to destroy it to access the fish above, and when cleaning how to prevent the mantis from just swimming out when you lift the lid to add food or clean debris and wreaking havoc. I fully recognize the premise probably wouldn't work but on the small off chance it might I would be very interested to see if any have had success with something of this nature.

#6. Lastly, this tank is glass and not acryllic and does not have modifications to allow a sump that is commonly seen, so for the time being I plan to use a canister filter. I am aware of the pros and cons but at this time I think it makes more sense that risking damage or paying insane fees to drill the tank. Without a sump area I don't know if I can use a protein skimmer which is highly reccomended from all the information I see. Could multiple hang on back skimmers for smaller tank sizes be used? Is there a good way to use a sump without drilling the tank?

Thank you for taking the time to read this and I hope you have a great day!

 

[Stomatopods17]

#1. It seems to be common practice to provide PVC burrows to give mantis shrimp the ability to molt in safety and darkness. My original plan given the size of a 90 for a mantis was to build a network of tunnels with pvc, like something you might see at the zoo for naked mole rats. However, a number of sources suggest that too many entrances might stress out the mantis or prevent it from molting. If this is the case, could multiple distinct, unconnected burrows be added and used by the mantis? Or would it just pick one and ignore all the others?

#2. Do the burrows need to be flat, or if a burrow started near the 'top' of the tank and worked down to the bottom, would that be sufficient? I had mused that as long as the mantis had at least one 'flat' burrow, the presence of a vertical burrow might incentivize it to explore the higher reaches of the aquarium instead of always sticking to the bottom.

First off, welcome to the hobby!
Never make a network of tunnels for 1 burrow, as for having multiple potential burrow locations, mine actually does have two viable spots but it favors one of them. Sometimes it'll dig a little canal under one of the other rocks to sneak through, but it never lives in them and only seals the burrow it prefers, if it wasn't for the occasion digging behavior I see I wouldn't consider it a burrow.

For the record, you should research what species of mantis you're getting cause there's only 1 species that's a 'true' peacock, the rest are very small <4-2" and likely won't use up the space of a 90 gallon. Smaller species will not use a network of tunnels and will basically mine a cavity in the rock and live in that cavity without relocating ever, some will venture, some will dig under the rock, but mostly once they have their spot that's their comfort.

Roy's List of Stomatopods for the Aquarium

O. scyllarus would be your true peacock, and for every real O, scyllarus I encounter at a fish store, its usually after 5 miss-ids ordered in, particular G. chiragra and G. ternatensis are often sent instead. This is why I actually do inquire for photos from anyone I order O, scyllarus for cause its very risky buying anything with a stock image or trusting an LFS to also check in with the wholesaler for an accurate specimen.

That being said, their care requirements vary and O. scyllarus (the true peacock) is especially finnicky when it comes to the aqua scaping as their burrow requirements are life and death. They construct U-shaped burrows with only 2 entrances and seal both those entrances off when it comes to molting. The burrow should be in mind of;

1: having only 2 entrances, anymore will stress the animal out and make it impossible to close up properly

2: be in complete darkness, again too much light exposure will cause it to stress and become more lethargic, on top of potentially shell disease growing.

This is why many will advocate for using PVC cause its very easy to have one piece with two elbows and have a structure properly sealed throughout from light spill going in, you can then hide it via covering with rock any way you wish while around entrances will be sealed off by the mantis's own preference. Its a very safe method of ensuring its requirements are met, and you might even get away with not needing the elbow pieces at all and just using a bigger piece half buried with sand and covered with rock that hide the entrance and let it come out of the rock a bit to build. The only downside is stagnant water flow but that can be remedied with random flow in the tank so the water occasionally gets a breeze inside. A 2.5" Inside diameter pipe should fit a full grown O. Scyllarus, 3" half burried would give it the best natural option for doing its own digging/wall lining inside. Black PVC is prefer if you can get it as it reflects less lighting, and I personally like to get a nail filer/sandpaper and go around the inside a little bit just to make the surface not as smooth for their legs to cling on better.

They do not hide as much as it sounds, infact with these conditions I always see mine either mostly expose peeping out, swimming around sneaking inbetween the rocks looking for prey items, or it actually approaches me from deeper in the burrow when it sees me get close to the tank and just stares me down. Only time they hide is when they're really exposed, they tend to just freeze up and not move around since their defensive positions are limited. O. scyllarus in particular is very active and I see mine always running around the bottom inbetween the rocks, swimming up and down the corners of the tank, sometimes when I'm sitting in my office it'll just perch on my gorgonian coral in the open and stare at me for a few minutes, or if i'm really unlucky when I go to sleep it'll be attacking the power head at the top of the tank keeping me up all night so it definitely ventures in there enough.

#3. What is the ideal level of flow / suggested powerhead(s) for a tank of this size for this animal? I have heard from some sources that having strong flow is ideal for water quality, but others state that low flow is required because a strong flow will stress the shrimp and keep it hiding all day.

Personally I never gave it much thought, with enough rock and space it won't feel the powerhead too much, and mine in a 29 gallon with a powerhead in mind of the corals rather than her means she gets around perfectly find with moderate flow. Stomatopods come from very strong waters, they're used to it, the only negative reaction I get from mine is she occasionally wants to destroy my powerhead and hits it, otherwise I've seen times where she's perched directly on top of it seemingly without a care for the flow itself. I do recommend flow either way, stagnant low-oxygen water will kill them more than high flow, some species actually can't live without it such as O. havanensis, a close relative of the O. scyllarus. O. scyllarus you mainly need to worry about shell disease and high flow tanks help keep the water filtering through the biological filtration that is your live rock.

Random flow from your filteration system, a wave maker, and either a protein skimmer or air bubbler if you option out of the skimmer will keep it happy.

#4. There seems to be general consensus that 'strong' lighting leads to shell rot, but what is the appropriate lighting threshold? Usually when I see this described a blanket 'strong' is used rather than a given number that could be used to purchase an appropriate light.

So to explain the disease better, with O. scyllarus particularly, shell rot grows on their carapace and can lead to killing them should it negatively impact one of their molts (it can develop anywhere on them, include close to the gills). Lighting is not causing shell rot on its own, it feeds the growth similar to algae. We do not understand the biological science behind shell rot, but correlation is tanks with high lighting are more likely to have issues with it while being unnecessary, while low lighting is less likely to cause it.

Truthfully, I run mine with 2 80% intensity kessils, if you don't understand what that means, basically I run giga high lighting enough to grow anything I want in the tank, I've had her for 7 months and she only develop 1 tiny spot of shell rot.. and it already is gone, cured, and never did anything negative. The trick is mostly your nutrients and the spectrum of your lighting, there's a reason reef keepers stick to blue mostly, white lights (which typically are your low lights) grow macro algae, diatoms, and whatever shell rot possibly is better than your standard high intensity blue reef lighting. A number you might see on a light is something like 10,000k, this is the color 'temperature' or 'kelvin', the higher the number, the more blue the light, while the lower the temperature, the whiter the light. Blue penetrates ocean water more which is why corals rely on it, but white feeds macro algae more as even small traces of that color temperature can cause photosynthesis for them. It would be safer to assume the 'weaker lighting' would actually benefit shellrot more than the 'better lighting' with high intensity of the color spectrum <7,000k for example. To them a 6 watt white bulb is more deadly than a 30 watt actinic bulb is my personal belief.

You're more likely to grow shell rot with your living room's ceiling light which usually is 2,500k-5,000k, or your windows than with some high tech adjustable high intensity lighting. The main trick is to just not have the nutrients for the shell rot to grow in the first place (nitrates, phosphates, and silicates.. research algae control and treat shell rot as such and I think you'll do fine without overthinking the lighting itself. If you're ever worried, just don't run light at all). In laymans terms, good water quality will let you get away with a lot more in lighting

Back to the O. scyllarus I have now, I did cure shell rot on her, but with that being said I have had O, scyllarus in the past that weren't so easy to cure... infact they didn't cure, the best cure is just prevention in the first place and this is honestly the first time I got to witness shell rot 'go away'. More often than not they arrive with the disease already established on them.

#5. This is by far my most out there thought and I completely understand if this premise is ridiculous but I wanted some input from those far more educated on the subject. Given the great size of the tank for a mantis, and relative inability to share space with tank mates, would it be in any way reasonable to divide the tank in such a way that the mantis has access only to the bottom half of the tank, and fish or some other animals have access only to the top half? I imagine that using panes of acrylic or plexiglass a sort of 'second lid' could be placed in, but I can see a number of issues. Keeping the second lid clean, keeping the mantis from constantly trying to destroy it to access the fish above, and when cleaning how to prevent the mantis from just swimming out when you lift the lid to add food or clean debris and wreaking havoc. I fully recognize the premise probably wouldn't work but on the small off chance it might I would be very interested to see if any have had success with something of this nature.

Splitting horizontally doesn't sound wise for a number of reasons. If you have the room vertically ain't too bad.

2/4 of my O, scyllarus lived with damsels peacefully.

First O. scyllarus; killed chromis day 1

Second O. scyllarus; a velvet damsel actually shared burrows with a giant male O. scyllarus without any aggression.

Third O. scyllarus; killed everything that twitched until my chocolate chip starfish actually killed it which I was not expecting to happen at all.

My current O. Scyllarus; damsel eats debris and left overs from her and often sleeps near her burrow, i almost think its intentionally for protection but I find it difficult to feel safe around the mantis. She's not particularly passive either as unlike my first and second O. scyllarus she hits anything that still bothers her and the tongs. 7 Months with no aggression is a pretty good run, I've lost more fish just by themselves in weeks in my life time, have the fish in before the mantis and see what happens. I wouldn't expect anything slow moving like a lion to work out however, damsels just weave in the rocks easily and are very fast, the mantis likely is just too lazy to go after it and knows its not worth the big chase.

I say just leave it as is and put a bunch of inexpensive fish like clowns and damsels in. Chances are the mantis might ignore them cause reality is fast moving fish aren't worth the effort when slow moving snails and crabs are an option and primary prey item to smashers. Dividing it will still leave the mantis constantly trying to harass upwards and fish constantly trying to sleep on the bottom panel if not being stress out by it, not to mention the complications of maintenance and water flow for the lower part. Research sump refugiums and you can stick something fun down there as well if you really want more inhabitants.

#6. Lastly, this tank is glass and not acryllic and does not have modifications to allow a sump that is commonly seen, so for the time being I plan to use a canister filter. I am aware of the pros and cons but at this time I think it makes more sense that risking damage or paying insane fees to drill the tank. Without a sump area I don't know if I can use a protein skimmer which is highly reccomended from all the information I see. Could multiple hang on back skimmers for smaller tank sizes be used? Is there a good way to use a sump without drilling the tank?

You want to make sure its not tempered glass, I drilled the back of my 29 gallon so I could install a sump/refugium bottom for it. You can use hang on backs but they're very unreliable and I've had my fair share of floods to know they're not worth it.

Infact this 29 gallon i originally designed in mind of a HoB overflow box and after 2 days of heart attacks I just drilled it with the rock and sand already in cause it once it was all done could stay happy.

Considering the expense of floor repair, buying different hang on back overflow boxes (they're like... 100 dollars for the box alone not including the plumbing and everything), I'd get a quota from a professional to look at it and give you a price, that being said there's still successful hang-on-back setups you can search for.