You said that you did a huge water change. You have a 14 gallon nano. If you had 0.50ppm phosphates and did a 50% water change with 0ppm phosphate water, then you would still be up at 0.25ppm. Unlike fresh water, lowering levels via water changes is not ideal for salt water. Unless you are doing +75% water changes every few days, however too large and/or too often of water changes will trigger another cycle. I would do a 5 gallon water change every 2-3 days. The tank will complete its cycle and be able to process the phosphates and they should go down.
As for phosphate reducing media, most of us use GFO (granulated ferric oxide aka clean rust) and tumble it in a reactor such as a TLF150 with a small Maxijet pump. With a nano tank, levels can change very quickly with the slightest change. I personally would avoid using a reducing media and just let your tank do its thing for another few weeks with water changes. It takes a little longer for a salt water tank to complete a cycle vs a fresh water tank. After about 6 weeks you should be doing water changes and by 8 weeks, your tank should be cycled and ready.