How many liters of clay pellets will I need for 40 plants?

Im using 6.25 x 6.25 x 8 inch square pots in an ebb and flow hydro system. There are 4 troughs each with 10 plants, draining into a big cast iron bathtub which is the res.

I'm buying the pots and the clay pellets online right now but I'm not sure how many to get. They come in 10, 25, or 50 Liter bags.

Also, can you mix coco coir with clay pellets in the pots? Has anyone tried this?

Dont mix mediums,it never works out well,plus having coco in a free flow system is not in the best interest of drainage.

Another thing,clay pebbles aka hydroton sucks,the shit floats,rolls around & is not a very good product,there are several other clay rock mediums,the one i prefer is called hydrorock,its made exactly like clay pebble products but larger & heavier,its shaped like natural stones so it all locks together after it settles in the net pot,it wont float out of the pot either.

Your going to need more than 1 50 litre bag of hydroton or other mediums to fill 40 pots,im betting you will need 3 of the big 50 litre bags.

One thing,make damm sure you wash the new clay medium before using it,if not you will have a hella mess,they say its pre washed but its nowhere near being useable right out of the bag,i use 5 gal buckets with several hundred 1/4 inch holes drilled in the sides & bottom,that way i can wash out the residue with the garden hose before ever bringing it into the grow.

youre going to need ~2 50 liter bags for those 40 pots