Nitrite, test kit, and Prime chemistry question

I recently waged a battle with blue-green algae (cyano) using erythromycin. It was a particularly stubborn infection, so I medicated for 8 days. I monitored NH3 and NO2 closely with an API test kit. Now at the end of the treatment my nitrite shot up to about 1.0ppm; ammonia is fine (I guess my nitrifying bacteria couldn't take it for that long...

Here's my question: I buffer with sodium bicarb, magnesium sulfate, and sea salt. I read that salt detoxifies nitrite to some degree. I also dosed with Seachem Prime, which says a 5x dose will detoxify nitrite. And I did a 50% water change. The fish seem alright, but I still have nitrite showing up in the test kit. It this a case where nitrite is present but "bound" in a non-hazardous form?

This is a 55gal Tanganyikan tank with 8 small fish and a BN pleco. Wet/dry filter + Aquaclear 50, established ~8 months.