forgive me as maybe i dont understand but i dont see why your looking to build a tank that big for keeping livebait for sea fishing, use a freezer lol. a 280 gallon tank will cost plenty to build with just the frame JMO wheres this tank going to go? 1272 litres of water weighs over a ton and thats without taking the glass and frame into account its a serious undertaking for even the most seasoned tank builder. just my opinion
you didnt add anything at the same time did you? i only ask because iv had it happen with a filter sock 5 mins after changing it went crazy and filled the whole sump with foam turns out its not that uncommon something to do with transport film on the socks themselves!
i would say the t5's will produce enough light if you place your hard corals high up in the tank ive seen some really good sps tanks using t5's so it can be done, with the price of leccy id think carfully before adding 3 x 250w halides as its gonna cost a fortune to run JMO
NEVER agree to the first price offered they will always offer more, now to push it up further cut adverts out of the autotrader with your car in same model and year(roughly) and send it to them proving to them that you cant buy a replacement car to your old cars standard for the money they offered and the final push ask THEM to find you a car to the same standard as your old car for the money they offered, it'l take a while probably best to let them write it off then buy it back for peanuts then repair it yourself that way should end up with cash in your pocket HTH