well 25 fish you will need a pretty big tank, somewhere in the hundreds could fit about 7-10 so you may need like 300 gallons + to fit 25 fish. But then again it all matters on size
well i dont know much about saltwater tanks from experiance and im worried the information will be wrong there are some things to follow
You litterally get what you pay, cheap stuff in the hobby will not work so you have to spend a good lot of money to get something to work.
Reef tanks need really strong lighting, for a 500 gallon tank you would probably need 4000-5000 watts of MH light with a high lumen lighting (lumens is how well the light matches the sun, incandecent doesnt match the sun at all so they have low lumens and metal halide lighting is very similar so they have high lumens, i think thats what lumen means
1 inch per gallon is not marine tanks just as a heads up, its something like 2 inch per 10 gallons (.2 inch per gallon) of fish but this rule isnt that good since you have to worry about territorial disputes
Ok just as a heads up, dont get the Simple Guide to Marine Aquariums book since it tells you what to buy, but doesnt say much on how to take care of the tank so its not a good book.