TANK MATIANCE FEES ? HOW MUCH ?

I am starting a aquarium maintained service and am trying to figure out how
much to charge. I have aquarium size as a variable and three types of
aquariums to consider. Reef tanks ( the most desired it seems and
expensive ) , salt water aquariums and fresh water aquatics. Any one know
where I can get a fee schedule to extract a scale that considers the
variables so I know what to charge ? I see people paying $ 300 a month for
a 100 gallon reef tank but how much for say a 300 gallon reef tank ? Or 100
gallon salt water aquarium ? or a 300 gallon salt water aquarium ? Or a
100 gallon fresh water aquarium or a 300 gallon fresh water aquarium ?
Thanks.

Robert G Smith