It can actually handle more than 800 gallons. This is the original design for the ETS-1000 skimmer which is considered a much better design when it comes to performance. It stands 5' tall and requires an Iwaki-70RLT pump.
my hsa 1000 can handle up to 1000 gallions its a beckett and needs a high pressure rates pump but you would be looking close to $650 - 600$ for mine sorry i cant do any better then that because i paid 700 with a waste chamber