One VERY TAINTED opinion here -- since getting rid of dinos after letting phosphates bottom out caused me the most effort so far:
-- extra feeding never worked for me so I'd vote start dosing nitrate
-- NeoNitro is fine/easy but expensive
-- my choice is Calcium Nitrate direct from Loudwolf site (with free shipping) but there are other options
-- if you do start dosing nitrate, keep an eye on phos as well since any process that's currently nitrate-limited could potentially kick into gear and (maybe) cause phos to plummet (((just something to keep an eye on,,, not necessarily going to happen)))
***if you already have plans to increase bio-load soon, though, that might change my thoughts