With a 2.5year battle with coolia and a 3 month battle with LCA, I have learned a little about dinos. I don't see any bubbles, so I'm going to take a guess that it is cyano, but being a low nutrient tank and only 6 months uoung, you are very lucky that it's only cyano. You need to start testing weekly with Hanna checkers and get yout nutrients up. I'd wager that the main cause of the cyano is not enough flow on the sand bed. Adjust your flow accordingly and don't use chemiclean. What I do and suggest you do the same is a weekly dose of Coral Snow (Calcium carbonate) mixed with the recommended dose of Microbacter7. This has been shown to be a better cure for cyano. I mix it up real good, blow off all of my rock with the return off, and after 5 minutes of shaking, dose. Let it circulate for a couple hours and then turn your return on. On the day that you do this, use a 5u filter sock. It should be full within 24 hours. Change back to your 200u filter sock at this point. Using this method keeps my cyano at a reasonable level and helps to outcompete the dinos. Once your rock is covered in coralline and nutrients in check, you are safe to use chemiclean although if you fix your flow and get nutrients in check, you shouldn't get cyano.