The advice so far is solid on.
Flow increase.
Lower nutrient input in food and city water. Old bulbs just make it worse.
IF you cannot throw the cash for RO/DI system at the exact moment. I would figure out a way (canister or even glorified trickle method in a couple mesh bags in wetdry) to run some carbon(approved saltwater kind not BONE) and some granular ferric oxide in 2 to 4 day intervals with the above advice by the esteemed fellows. (leaving the carbon or GFO for extended period can become inhabited with ammonia and nitrite feeding bacteria which will compete with liverock and can spike nitrates or = more algae food)
Using the carbon and or GFO could be used as a stop gap for now as far as lack of RO/DI water. And it would help get your nutrient levels down and offset the issues coming in with the city water you are mixing with your salt. ALSO, I didn't see this mentioned, If your wetdry has media in it for bio removal...bio beads, balls, stars, floss or the like remove it. It will house the same bacteria mentioned above and compete with liverock and cause algae food/nitrate.
2 of my tanks have trickle filters that are used as glorifed sumps. They have empty trickle areas. I place a bag of each (carbon and GFO) below the input of tank water on the eggcrate shelves that normally were designed to hold bioballs to help pull nutrient levels down. I have even used an inverted 2 liter bottle suspended below my skimmer output in the sump to house carbon or GFO in one of my other systems that is just a sump. This in conjunction with water changes help keep nitrate and phosphate levels in check.
Hope you are able to get the levels down.
btw...I hate it when my Aussie is acan.