hi
in my opinion you can never have to much air during the summer anyway, in winter when temps are 10c and below water is at full oxygen saturations so no real need for extra air however i keep it on to keep the bio filter alive
as for it effecting algae all i can say is my blanket weed didnt like it
i had a bad case earlier in the year i was going to treat with a blanket weed control so i swapped my winter 25lpm air pump to my summer 70lpm air pump ready to treat but within days of putting the big air pump on the blanket weed was dying off so didnt need to treat after all (thank god cos i dont like putting chemicals apart from dechlorinator in to the ponds unless i really really have to)
you dont have to have a lot of plants in the pond i have one in my koi pond
but i have 8 in the goldie pond
but plants do fight the algea for nutrients and sun light
they may put oxygen into the water during the day but at night they use up the oxygen they put in (mainly the ones where their leaves a submerged)
and yes algae can effect your ph found this
http
/www.garden-pond-filters.com/garden-...lgaearticle.htm
the part about the effects on ph reads
As algae blooms and other algae varieties die off they fall to the pond floor where they start to decay. The decaying process produces carbon dioxide. The increase in carbon dioxide acts as a food source for the remaining algae, starting the process off all over again. In addition the carbon dioxide that is used up by the algae increases the pH level of the water. This increases the level of ammonia and decreases the level of ammonium. Ammonia is potentially lethal to aquatic life forms in high doses
glad your getting it sorted you have to share some pics with us