Algae is toxic and if ingested may cause illness and possibly death.
Photosynthesis requires light to grow algae, limit the light equals limited algae growth.
Make sure your tank is opaque to limit light to your water storage tanks.
PH either base or acid beyond neutral can cause problems with your water, adding heavy metal to your drinking water, extracted from plumbing used to move water through your home or system.
Test your water as often as possible; most pool supply companies will test your water for free... listen and integrate...
Black polyethylene plastic and opague fiberglass tanks are a natural for storing water under 50,000 gallons, outdoor storage, natural white for indoor applications. NSF, FDA, NFPA certifications.
Fiberglass with gelcoat, is a good solution to 50,000 gallons. FDA, NSF, NFPA and AWWA
Steel in either welded or bolted steel and a good storage vehicle larger water storage applications from 25,000 to millions of gallons of storage capacity. FDA, NSF, NFPA and AWWA
The American Water Works Association provides standards and specifications, http://www.awwa.org for assisting you in the development of design.
There are various types of algae, none of them are a good addition to your diet in their raw form.
This article and pictures were submitted and included in http://www.wikipedia.com under Water Tank...
Designing water tanks, requires many considerations.
A... Drinking water for home and cities, polyethylene, fiberglass, welded and bolted steel. AWWA, FDA, NSF certifications guide successful construction and maintenance protocol.
B... Agricultural water considerations include water source, and since the quality water may vary as irrigation and farm animals requirements are different. Animals require clean water, which can originate as rain water, creek or river water, but must be treated to maintain freshness. Materials of construction include clay lined pond or lakes, cisterns of concrete, polyethylene or fiberglass. Above ground storage in bolted steel, welded steel, fiberglass, plastic polyethylene, fiberglass. AWWA is a good specification for general water storage.
C... Fire water is stored in a variety of materials with a wide variance of storage and accessibility functionality. NFPA (National Fire Protection Agency) projects a number of compliance requirements. This specification focuses on presenting a consistent source of fire water to the fire department agencies.
D... Water for food and chemical production, may require additional treatment to meet requirements, Deionization ( DI ), Reverse Osmosis ( RO )
Consider that any water storage tank system is subject to contamination. PH, Algae spores, viruses and bacteria may see accelerated growth to the your storage tanks. Accelerated bacteria growth may cause your stored water to go septic, and grow things you would not want to ingest.