Think I am qualified to answer this (I hope

)
is it jsut for SPS?
No its for all system corals and inverts including live rock fauna
Can this unit run for softies and LPs?
YES
What does it exactly do?
It is a ULN system so it lowers your nutirents as well as providing increased growth of corals and colouration as well as providing a diverse food source for your whole micro eco system
what happens if you suddenly stop?
In time your nutrients will rise and your tank will go back to pre dosing conditions, no it wont create any crash.
How much Algae do you need or do you need any?
?? None
So for a 250 gal tank-
what would it cost is it monthly or semi monthly
Start up costs too.
each 30amp kit is $59.95 for your size tank you would be dosing every two weeks
1 x Bio Digest
5 x BioPtim (or 1 x gamma size vial)
5 x Reefbooster (or 1 x gamma size vial)
same for stronti plus and Iodi+
Gamma size is $119 for 10 vials.