how high is through the roof? how much live rock is in the tank? which corals have you been attempting to keep? :) do you understand the nitrogen cycle? your overstocked but is there also a chance you could be overfeeding?
id jus start weekly 20% water changes until you can bring your nitrates down.. id also recommend a protien skimmer and once fitted go for 10% changes..
on my 300l tank i had 6x24w t5's + 3x39w t5's with a mixture of whites and blues and 2 pairs of aquarays that i ran for 9hours a day..
before you buy anything else you need to look at your lighting.. Id also put your lights on for 8 hours and not split if your keeping corals..
I also recommend making your own water too if at all possible.. unless you can be sure your getting good quality water.. you want the TDS reading to be as close to 0 as possible and you want the salinity to be the same each time.. do you buy fresh RO too? and do you own a hydromoter or refractometer? for topping up with fresh RO?
you should be able to pick up a second hand light unit for alot less..
do you know your nitrate and phosphate levels? high nitrates and phosphates are usually the cause of algae.. phosphates can be introduces through bad quality water or food.. if using frozen try to rinse it (i'll admit i dont bother myself, but i do make sure i drain the water out when its defrosted) are you using a good quality flake? :)
i wouldnt worry about trying to feed the shrimp.. it'll find food..
What type is the surgeon? it sounds like your probably overstocked which wont help with water quality (again check nitrates) my bangaii's wouldnt eat flake either! :(
what corals are you trying to keep? and how long have you been running one blue t8? i find it hard to believe you've got to the stage where your dosing without having adequate lighting.. you've been terrible informed :(
you need to find out the cause of the algae problems rather than starving the tank of light.. the corals use photosynthesis so turning off your lights for a long period of time is a big no no.. where are you getting your RO? what stock do you have? are you over feeding? etc..
i had 100's of them at one point.. i dont rate anything other than digging a big hole where they stand! but thats just from my experience.. ive got a 50+ kg of dead rock in the garage to show that aiptasia beat me!