BTI briquets are "donuts" that float on the water's surface where immature mosquitoes reside.  They are often applied to areas difficult to access and can be broken up for use in small areas.  In large areas, it is important to ensure that these products remain where they are placed.  They can be anchored down with string, slipped over a dowel rod, or other means.  They should last approximately 30 days.

BTI granules are good for short term treatment of accessible areas and are perhaps the most widely used larviciding product available. Aquabac can be somewhat labor intensive as you must continually monitor and retreat areas as necessary every 7 to 14 days.

BTI granules with a long term formulation.  Lower your labor costs with Sustain.  These granules are twice as strong and can last up to 30 days.  

Highly selective microbial insecticide containing Bacillus Sphaericus.  Effective against mosquitoes in a variety of habitats including polluted water.