Is my filter media enough?

[glb]

I have a 12g nano that crashed last summer after our AC went out and it reached 92 degrees for three days. It wiped out my coral but the fish survived. Since then I had a multitude of problems, including cyano and a huge red hair algae outbreak. After my remaining fish died, I recently cleaned off the rocks, did a massive (90%) water change and let the tank go without lights for a week. Now I have hermits doing well and am planning to add fish. In my sump I have sponges, purigen and Phosguard. Since the tank won't be this empty again, now is the time to make changes to my filter media. I don't have a slimmer. Can anyone suggest an addition to my filtration that would be helpful or is this enough? Now is the time to do it. Thanks!

 

[glb]

Ammonia and nitrites 0, Nitrates 5ppm. Ca, Alk and Mg all normal. SG 1.024. Temp 78f. Phosphates .17 probably because it was feeding the algae before and algae is gone now.