It would have to be huge and with good ventilation otherwise skin problems may develop.
Also bare in mind that five snakes will quickly turn the water it into a cesspit.

With the help of water plants,snails,frequent water changes and a good filter you could deal with the waist of one or two snakes.

This type of set-up may be better suited to Nerodia,Natrix, tropical water snakes (Liophis,Xenochrophis ect), semi aquatic 'phibs and Lizards.

Good luck with your project!