hello Babesbarn, and welcome to HCP!
It's always good to hear of a crabber that's done some research and is really trying to do the best for their crabs. And no worries, we will be patient as can be, we were all once in your shoes, and know how it feels! I had my hand held through several events with my crabs, trust me I know how it feels.
So to answer your question, there are a few things you can do. As Gizaroo2 mentioned, you should be offering BOTH fresh dechlorinated (or distilled water - if you use regular bottled water you still need a dechlorinator that neutralizes heavy metals, the same as with tap water) and ocean salt water. Many are finding it is easier to do without the sponge, as it can harbor bacteria so must be sterilized every two days at least. Those who do use sponges generally have two so they can trade out every other day. This gives the sponges time to dry after being sterilized, further inhibiting bacteria growth.
Your crabs will thoroughly enjoy water dishes in which they can fully submerge and bathe themselves, as well as to fill their shells with water. They carry water in their shells to help keep their soft abdomen moist and also to help moisten their gills.
The only real reason a sponge might be needed in a water dish is to help add humidity to the air, and perhaps be a snack for the crabs. The crabs do benefit from the cellulose in the natural sponge. Cork bark, coconut husk, mopani wood, and grape vine as well as maple and oak leaves are also excellent sources of cellulose for your crabs.
As for the shells, if you have a crab that does change out of a painted shell into a natural one, remove the painted shell immediately. Regardless of whether he found the painted one more comfortable, the paint itself is not safe for him. he will eventually settle on a shell with which he is comfortable, and you have removed a hazard from his home. This is why you want to be sure and offer a wide variety of shells, at minimum 3 shells per crab. I tend to offer at least 20 or 30 shells in my tank of 14 crabs, though with 5 crabs I would probably offer the same.
it's fun to shop for shells! lol. For people and crabs
I get most of mine on Ebay.
