The water clarity shown in the picture indicates to me the filamentous algae(FA) grows on the bottom down to around 5 maybe 6ft deep. Thus all pond bottom areas less than 6ft will produce your algae growths that eventually break loose and float. Once floating those floating clumps are basically done growing and waiting to die due to some reason and sink, then hopefully they decay and or create lots of bottom muck. New appearances of FA are always from more mats breaking loose from the bottom.

Cause of the algae growth is due to excess nutrients in the water that are not being consumed by other plants. If the pond had lots of submerged plants to use the nutrients, water would be very clear and weed infested. The more nutrients that present the more plants that will grow to use those nutrients. Nature demands some sort plant grow to use available nutrients. Nature has thousands of different pant species available to grow in all sorts of nutrient enriched conditions.

Filamentous algae(FA) grows because more dissolved nutrients are available than being used by all other forms of plants that are present. Tree leaf litter entering the pond each year contributes lots of dead nutrient laden material that when decomposed releases those nutrients. Natures policy. Waterfowl manure also adds lots of nutrients. 10 geese make the equivalent manure of one cow. Geese are FLYING TOILETS.

When one uses pond dye its purpose is to reduce sunlight penetration. Reduced light from dye if used properly reduces the amount of algae that grows in water deeper than 2ft. The water needs to be around 2ft deep and dye dark enough to filter enough light to suppress algae growing on the bottom. As per label the concentration of dye should be around 1 part per million. This, when using the gallon container size, is same as one gallon per million gallons of pond water. If less dye is used then less algae or fewer rooted plants will be suppressed. FA growing deeper than 2-3ft is a good indication the dye concentration is not dark enough. A little bit of dye should be added monthly to adequately compensate for: dye evaporation, dilution, UV fading, chemical decay, and absorption into sediment and organics. Dye is an organic stain. It naturally and gradually breaks down and dissipates. I recommend the small monthly amount be applied in Nov-Dec and again as soon as ice melts in spring and also monthly. Monthly dose is 1/10 or 1/12 of the original volume treatment. Remember dye is used for pre-emergent treatment for plants. Dye does not kill the plants.

Filamentous algae always starts growing attached to the bottom or on solid structures wherever it receives enough light for growing. Thus dye should be best used before the algae is growing i.e. as a pre-emergent. It does not control floating algae mats, already well established bottom FA and submerged plants, or emergent (shoreline) vegetation. Floating FA is best removed or treated with an algaecide. Heavy hard rains, strong waves often beat-up the floating FA and it sinks.

FA of one species or another is usually a continual problem in shallow areas of ponds. Often FA does not grow in the deeper central bottom area of ponds due to lack of adequate sunlight. Tilapia are the sheep and goats of the pasture keeping the FA trimmed and eaten.