The pond dating
This is a common algae in new aquariums (including marine tanks), especially aquariums that have not fully cycled as this leaves many available nutrients for these diatoms.
If an established aquarium struggles with these diatoms, this is often an indicator of excessive silica, poor mineral/electrolyte balance, an unstable biological aquarium environment, which in turn is often caused by poor filtration, poor cleaning procedures, Redox balance, inadequate aquarium lighting or over medication.
The information contained herein is based on my experience with literally 1000s of contract client aquariums over the years, as well as research, and feedback from other aquarium keeping professionals.
Please note that algae control is NOT an exact science and there are many methods I have not used or researched that may also work.
This is the algae that coats the front and side glass.
Many of the methods cited here for algae control address the bio filter, but some do not and those that do should be used first based on my experience.
The bottom line is I do not claim that this article is the "end all" for algae control, but I do think the majority of readers will find this article useful, often with information not found elsewhere.
Green Spot Algae is often eliminated with increasing phosphate levels in your water.
Try to maintain at least 0.3 to 0.5 of phosphates throughout the week and more preferable is in the range of 1.0 - 2.0 ppm of phosphates (however this algae is considered normal in small amounts).
Finally as per Silicates, do NOT confuse these with silicon/silica, as the later is inert while Silicates are not!