Hey there! Long time no post. Anyways, I have a small "critter keeper" I picked up at a local pet store. It holds probably 1-2liters of water. Betta in it died roughly 3 weeks ago since I emptied it and now I have nothing in it. Can I put a fiddler crab in there? Any other suggestions for the critter keeper would be appreciated. Also I have a 5g empty I was thinking of putting sand 1/4 the way up and have it sloped into water. For the water do I need to have a filter? I know I need some aquarium salt for the water.