Fish tank for my science teacher...

There's alot of variables you'd need to know, like...
Is it just a bunch of fake plants?
What kind and how many filters that need set-up.
Kind of substrate?(Flourite compared to a bag of candy coated gravel)
Etc's.

I'd imagine a "professional" would charge $50 just to show up, and maybe cover the first hour.

Personally, I'd try to look at it as a learning opportunity. And look at it as more of a RAOK. But if he insist(he might not be able to stand to not give something) on paying something, just offer $10-$20.

EDIT:
Or tell'eem $50! lol

Well, first off, figure out what he wants. Some set ups take longer than others. For example...hegh tech planted vs plastic plants. FW vs SW. FW vs brakish. Even someone as simple as filter type...canister vs sponge or ug.

Second. Make sure he picks up the cost of all supplies. Do show him the short cuts and cost savers...$1 tank sale, used vs new, pool filter sand, etc. But not out of your setup cost.

Third, figure out what your time is worth. What do you get paid per hour at your normal job? How long would it take you to set up his tank?

Fourth. Offer a fixed price. In your mind the tank will take x hours to set up at y rate. Charge him Z. Now, when you set it up, don't count the hours. Take your time to explain why things are set up the way they are, what you are trying to achieve with media placement in a filter, why you scaped a tank with certain plants in the back, etc. It will help him to know the why so he doesn't try to screw something up later.

Fifth. Make sure he is good on the maintenance or offer to take care of it for him...possiblly for a price. Especially if this is going to be a class tank, teachers seldom have enough time in the week to worry about water changes. Good thing he is a science teacher...they typically grasp nitrogen cycles and water quality issues better than English profs!

Just make sure that you can help choose the stocking and explain to the 7 year old why some fish will work and other won't. My 7 year old would love to put an Firemouth or Oscar in my planted small fish tank. A little bit of explanation goes a long ways to preventing the stocking from being a goldfish, angel, 20 neons, 15 guppies, 10 mollies and a common pleco.

i'd say just charge $10-$25 besides supplies........or a ROAK.....maybe extra credit if you need it

go for an even $30 something is better then nothing.

Yeah, I would say around $20-$30. Think about it, if you set that up in an hour (idk how long it would actually take) you would have made $20 in an hour. Not bad at all, the only problem with that is you dont have another few hours a day to go along with it.

I dont know how hard it is to set up a nice looking planted tank, but you dont want to over charge your teacher.