Off to a good start! Very proactive!
OK, so if it were me, here is what i would do:
ID the type of cyano you're going to be battling
Add a powerhead (preferably one with an irregular flow such as a wavemaker, I've used Jebao powerheads with good success if budget is a concern)
gently gravel vac the substrate to remove any debris on top (with all flow off so as to not spread around) I ran a Jebao PP4 in my 20 Long with good results
Get a full reef test kit (N03, PO4, Alk, Mg, Calc to start) Ph may need to be monitored, but that's at your discretion (i personally dont, but now that i'm having an issue, i may)
SLOWLY dose necessary additives to bring your levels to ideal and work to maintain them constantly
Add an in home RODI unit and get a cheapie TDS meter so you know exactly what you're adding to your tank (
amazon has a TDS meter relatively cheap, i think like $12, if you want to snag that first and test the water coming from your LFS, if getting 0TDS, you could procrastinate the RODI unit a bit more, but i consider them to be a staple now)
Check the specs on your lighting and see where they compare to quality reef lighting. (what dimensions are tank and i can make some recommendations if like (again, they would be purely personal choice with budget in mind)
Monitor your NO3 and PO4 closely until comfortable they are not high. You don't want 0 and 0 readings as that will starve your coral. IDEAL but not always attainable in a system containing the corals such as what is in yours would be NO3 2-5 and PO4 0.03.
Add Chemipur Elite to the filter media
Do you have a skimmer? (not a necessity by any means and there are many successful tanks ran without one, but will help battle nutrients by removing prior to breaking down)
Aside from that, just research, research, research. Even if it's not something you have a problem with now, it may pop up later and better to be prepared than scrambling for a solution as I'm currently doing for my issue. I hope this helps and again, this is simply my train of thought and course of action i would take. Always work to the root of the problem rather than masking with additives and prettiness. Here for ya if need anything else or any other questions, but that should get things back on track.