can crabs and marine fish live togeather in tank

yes. hermit crabs are often used as reef tank janitors. you can read more about them here:

http://saltaquarium.about.com/cs/aboutj ... 43099n.htm

yes. hermit crabs are often used as reef tank janitors. you can read more about them here:

http://saltaquarium.about.com/cs/aboutj ... 43099n.htm
thankyou for you response i thought hermit crabs needed air and water good to know they can live soley in water
i was alos wandering about crabs from the beach my partner thinks they would be ok but im concearne dthey would eat the fish if they are ok what size is ok if not why?he has put some in my tank at the moment there doing ok but i hav eno fish in there yet we are just begginning our aquarium also are beach rocks ok we are in vic mornington peninsula australia this is where we got the crabs and rocks i havent teate dph levels ect yet i have to do that next week if all is good with levels do you think fish will be ok to put with crabs i have at present or should i remove them?

well it isn't good to put any outside fish into your aquarium. they can carry deseases and put your other fish in danger. i would take thoughs out righ away. also yes they could harm your fish because they are more aggressive then the ones you would buy at the store. i hope this help you.

I'm not familier w/ aqua pods but i'll try and help. Did your water level drop below the pump? This would make the pump suck in air. If you have a skimmer many medication and additives can cause them to create micro bubbles. Sorry i couldn't help more :(

you will need about 7kg of live rocks and for the cycling period it ranges from a couple of weeks to much longer. get the basic test kits to help you determine when it is ok to start putting livestocks in.

basic test kits would be yr kH,pH,ammonia,NO2 and NO3. oh dont forget to get a hydrometer to check salinity. :P do check your temperature too.