Crab Setup, Lots Of Questions

[Zante]

I have an empty tank I would like to use for crabs. I have a few ideas for the scaping, but I would like some input.

The tank has a footprint of 60x35 cm and is 40 cm tall

Is it worth using real plants or will the crabs eat them?
If I use real plants which would live in shallow brackish water?
What about the land part, which plants would be fine in brackish soaked sand?
How many can I fit in the tank?
What proportion of water to land?
Heated water, heating lamp or both?
If heating lamp do I keep it on permanently or on a timer?
I was thinking, as a rule of thumb, of using two cups of marine salt to 20 litres of tap water (300ppm from the tap). Is that ok?

I understand the answer to these questions depends on what species of crab we're considering. I had red claw crabs in mind, but I welcome any suggestions.

 

[raptorrex]

I have an empty tank I would like to use for crabs. I have a few ideas for the scaping, but I would like some input.

The tank has a footprint of 60x35 cm and is 40 cm tall

Is it worth using real plants or will the crabs eat them?
If I use real plants which would live in shallow brackish water?
What about the land part, which plants would be fine in brackish soaked sand?
How many can I fit in the tank?
What proportion of water to land?
Heated water, heating lamp or both?
If heating lamp do I keep it on permanently or on a timer?
I was thinking, as a rule of thumb, of using two cups of marine salt to 20 litres of tap water (300ppm from the tap). Is that ok?

I understand the answer to these questions depends on what species of crab we're considering. I had red claw crabs in mind, but I welcome any suggestions.

if we are talking Redclaw or fiddler.

both live their, active lives, on dry (almost) land. so i would suggest a 1/3 water 2/3 land setup.
I'd go for fake plants. crabs will damage and then eat some live ones.
and I'm a strong advocate in walking before i run. (get the crabs happy, then try some live planting.)

I'd take the land up to halfway in the tank then add a small slope towards the side. but keep it well clear of the top. crabs are adept climbers!.

its more complicated than just filling the tank with land and water.
you need to work out how to keep the "dry" area damp. but without swamping it. not to mention how you separate the water and land.

can i make a suggestion?
spend some time, if you can, and watch some wildlife films of these guy, and how they live. You will find most on fiddlers, but they are broadly the same.
this may well help you decide just how they may be best kept.

you can of course just put them in brackish water, and give them somewhere to crawl out. that is dry. and it seems they will survive like that.
however, as with all stock, looking at their natural environment is very revealing.

i will, if you wish, post a more detailed suggestion. but be warned, its not easy and you need a fair amount of "diy" skills. not to mention a fair dollop of common sense. (no offence mate. but i find some find my common sense, advanced knowledge)

 

[Zante]

My plan for scaping was to build a kind of sloping dam with stones to keep the land at bay. Build a beach behind the dam with sand and a little bit of shingle and a few rocks.

The beach would keep damp from the water seeping into the sand through the stones in the dam.

Included in the construction of the dam I'd put pieces of wood so that they would be partially in the water and partially sticking out of the beach.

The design I have in mind makes sure there is nothing closer than 15cm to any edge of the tank.


What about the heating?
Would heating the water be enough to keep the land area warm or do I need to get a heating lamp?

 

[raptorrex]

My plan for scaping was to build a kind of sloping dam with stones to keep the land at bay. Build a beach behind the dam with sand and a little bit of shingle and a few rocks.

The beach would keep damp from the water seeping into the sand through the stones in the dam.

Included in the construction of the dam I'd put pieces of wood so that they would be partially in the water and partially sticking out of the beach.

The design I have in mind makes sure there is nothing closer than 15cm to any edge of the tank.


What about the heating?
Would heating the water be enough to keep the land area warm or do I need to get a heating lamp?

heating for the water and land, yes.

i see what you are thinking. but the sand will wash into the water, honest i have tried.

as far as i can tell you need to make the land and water, totally separate. then direct the water, from the filter, onto the land and back into the water.

my first thought were a pile of sloping sand, leading to the water. thing is though, the sand would wash into the water and play havoc with the filter
I suppose you could use uncycled water, and do daily water changes. but there would always be some water left behind. so i am uncomfortable with that. and in reality the water would undermine the sand, anyway.

so, i suggest (here comes the DIY) building a glass shelf, roughly half way up the tank hight. extending to where you want the waters edge to be. at a slight angle sloping towards the water.
on top of that i lay a covering of big gravel, probably best called pebbles.
on top of that goes a layer of water permeable membrane.
which is topped off with the sand, used as a beach.
water should run down the self, without washing the sand away. but still keep the sand damp.
some sand will, inevitably, wash into the water, but much less than the uncontrolled version. and you should be able to keep most of it out of the filter.

you can either leave the whole area for water.
or turn the self into a box and partition off the area under the land.
i prefer the latter, and cover over the empty area. this makes the tank a good bit lighter, which is always good.

for filtration I'd suggest a small, or even not so small, external cannister,. like a Eheim 2213.

 

[Zante]

This is very schematically what i was thinking of.
I have omitted all pebbles, rocks, wood and fake plants that are not structural.
This diagram is just to give an idea of what my idea was.

For the internal filter i was thinking something like a Fluval U2 or similar sized.

I thought of using slate because it's so easy to stack with very little in the way of gaps, and that would help to keep the sand on the beach.

 

[maurizio]

Talking of "how they live", just a little contribution, to shown an alternative: in this environment, the land was nowhere to be seen, at least at a crab's walking distance!

 

[raptorrex]

Talking of "how they live", just a little contribution, to shown an alternative: in this environment, the land was nowhere to be seen, at least at a crab's walking distance!

there must be land somewhere close, the sleep under it. as its tidal, its below the water at least twice a day, for some time.
but you can take the mangroves as "land". and remember not every Redclaw lives in identical environments

the major point being. they dont live in the water, but around it.

 

[raptorrex]

This is very schematically what i was thinking of.
I have omitted all pebbles, rocks, wood and fake plants that are not structural.
This diagram is just to give an idea of what my idea was.

For the internal filter i was thinking something like a Fluval U2 or similar sized.

I thought of using slate because it's so easy to stack with very little in the way of gaps, and that would help to keep the sand on the beach.

oh yeah. its an interesting idea.

i like slate too for partitioning. indeed it tends to be recommended by those who make this sort of thing.

I must admit I'd never put any substrate in the water section.

I'd still be worried that the sand would wash out/undermine, though.

only one way to find out! give it a try.