Green Spot algae
The 3rd photo is made with a macro lens. Those green dots are smaller than 1/2mm.
Green Spot Algae prefer direct light. It forms green spots on aquarium glass and slow growing plants that are exposed to strong light. This algae will appear if CO2 and Phosphate (PO4) levels are low. Since it is very hard, algae eaters can't do much in eliminating this algae. Neritina Zebra snail is the only algae eater known that can, literally, eradicate the Green Spot Algae. It can be scraped manually off of the glass with a razor blade. In a case of an acrylic aquarium use plastic razors only. This algae is considered normal in small amounts.
To prevent this algae keep stable CO2 levels, dose NPK regularly and improve the water circulation throughout the tank for better nutrient transport. Keep slow growing plants in places where they will get less light.
Posted by Dusko Bojic aka Che Guebuddha at 11:49 AM