It sounds like you would make a really cool looking rock river bed. But crayfish want sand. To test this, try one tank with rock and one with sand and decor. Then sit back and watch. Who is active, productive, busy? That's a happy crayfish.
Sand is sold at fish stores, even in colors.
Here in S. Louisiana, blue and orange crawfish are sold for around $20 when available. White is not, so I would have to order for more money and have it shipped. A white cray on black or blue sand would look awesome.
They need space: a 10 gallon would be absolute minimum for one. It really should be 20g (some here would say that anything under 20g is out of the question).
They don't eat much. This is where concerns about a poopy tank can be put to rest. Just a weekly water change and the occasional vac will do it. Unless you add other creatures (if you go my goldfish route, as mentioned previously, goldfish are very messy and you'd have to vacuum more often).
Daily food:
-Just a few (3-5) pellets of crustacean food. Hikari Crab Cuisine is the Cadillac of these. If you go for a different brand, make sure A.) It has as much or more protein as Hikari (over 30%), and B.) It contains no copper. Copper kills crustaceans.
-Algae tab. If it's a baby, 1/4 tab per day. A juvenile (has undergone 1-2 molts), 1/2 tab. Anyone older, a whole tab. It's like their cookie: watch them spin it around and nibble the edges.
-A green pea (or occasionally a carrot) from frozen. Run it under hot water to defrost, break the skin of the pea and squeeze out the inside so it will sink and be accessible. If you drop it in directly above them, it's fun to watch them dash out to grab and drag it into their lair.
This is another reason why sand is their element: all the little daily foods can easily drift between and beneath rocks, becoming inaccessible and rotting. On sand, the cray sees it or stumbles upon it exploring and, with her little legs, starts processing and eating this delightful surprise.
Twice a week:
-1/4 to 1/2 of a frozen shrimp. Run under hot water like the pea. Less may be needed if they don't rush out to claim it, more if it's after a molt. Just watch their behavior - they'll tell you.
Once a week:
-A blanched vegetable. Zucchini tops my list, followed by cucumber and romaine lettuce. I avoid broccoli, cauliflower, onion (too stinky, disintegrates fast). No one ever seems to like bell pepper or celery. Cuke does have some calcium, so does zuke, but their main source is that Hikari.
How to cut: just one 1/8" slice of zuke or cuke will do it. Lettuce, 1/8 of a leaf or a little less.
How to blanch: blanching is boiling for 1 minute. It's fast and easy. Boil a bit of water, like 1/2", in a small pan and place the veg in for one minute. This breaks the surface fibers to allow access for aquarium creatures. Pluck it out, let it cool. Don't rinse. You'll need a chopstick or skewer to poke through it, to anchor to the bottom, otherwise the veg will float.
You want your cray to have a reason to come out of his hidey-hole and hunt his food, nibbling and working at the vegetable until he can break it free and drag it back into his lair. They also like to play with the chopstick, so leaving it in for a day or two is okay. I don't know what that's about. They just really like to have fun and play.
Right now, it sounds like food/poop might be your #1 concern and environment is #2. But it's actually the reverse: they need lots to do, but they don't eat much. They need a sandy bottom with plenty of hiding places and moveable activities to keep busy all day (and especially at night: they are nocturnal, so don't be surprised if you wake up to find his entire realm turned upside down. If you put it back they way you carefully set it up, he'll get really pissed and work twice as hard the next night to put everything back the way HE wants HIS home. Try to see it his way: would you want some giant rearranging your furniture in a way that doesn't suit you?)
If you see a crawfish never doing anything, it's because they're not being given something to do. Setting up an environment that will keep them entertained (and then they'll definitely keep you entertained) is the primary step. Food is the lighter end of crawfish duties; it's easy to drop in their daily-weekly requirements. If you don't have time for a blanched vegetable every week, no big deal. Do it when you can. Some people don't feed vegetables at all. Just for some perspective.
The requirements for all varieties are generally the same. Some Asian varieties like a bit more vegetation, some individuals like more meat than veggies, but like children they'll let you know by ignoring what they don't want and clamoring for their favorites. BTW, one way a cray lets you know it's hungry is to stand on its hind legs and reach up when you come near. Aww, so cute, you think he's saying hello. Nope, he's saying "Feed me, you giant!"
