how do u buy your nutes? quart? gallon? 2.5 gal? 5 gal?

just wondering how u guys buy your nutrients. i bought the quart size and have been using them for about 6 weeks and starting to run low. i know it kinda depends on your rez size and all how much u use at a time.

I buy mine in litre bottles.

If I do my math right I have around a 6GAL (30L) res and 1L is around a quart (I assum a quart is 1/4 of a gallon? )

I've had some stuff begin to grow a mold or something on top of the nutes.

Just calculate about how many nutes you'll need based on the size of your
res and when you want to change out. That way you can make sure you
still have enough, but wont have too much and it goes to waste.

Any size other than a quart, that shiz is a straight rip-off.

so by the gallon seems the way to go for a home grow. cool. thanks guys.