Not another algae question!!!!

[PJFISH]

Sorry for the one billionth algae question, but here it goes! I recently added co2 to my tank and dose 16 ml Excel daily but I'm still getting these small spots of algae on rocks, glass and some plants. They're really hard to scrape off and green, not sure what kind. I thought co2 and excel would keep it at bay? What should I do? My lights are only on about 7 hrs a day, is there some crazy nutrient deficiency? What do I test for? HELP!!!!

 

[Old Scales]

Test NO3 and PO4. IF CO2 is enough and light is not too much, then playing with the balance between NO3 and PO4 is a possibility. Too much of one and not enough of the other or vise versa can cause different types of algae. Try for 10-20ppm NO3 with 1-3ppm PO4 and see if it helps. The paranoia about really low NO3 has caused many an algae outbreak. Regular weekly WC's seem to help also. OS.

 

[PJFISH]

Thanks, OS - I do regular 50% changes and within 3 days of scrubbing the glass, it's back with a vengeance! I'll get a test for PO4 and keep an eye on nitrates.