Cannaboost with a 250l system.

i have a 250l system and want to run cannaboost.. which is throughout the whole flowering period.
i use DWC

it says to run 2ml per liter... so that 500ml.... which works out at £25 every water change (£50 per litre)... which i do every week.

which would = £225......... surely there is something i can use to boost my buds other than this?

anyone use the canna aqua range with an alternative booster?

How many plants? Most people I'm seeing now have realized they can use another type of PK 13/14 for much less money that does the same thing. Look up cheaper products and cross search it with cannabis. I'll bet that you find what your looking for. However there's sure to be someone to help that has been through this exact thing.