From the description of lighting , I believe u are able to keep clams in the mentioned spot.... The sun light is enough.....
I can forsee a few problems
. Sunlight heating the water too fast your solution of having fan is OK but bear in mind clams especially maxima do not really tolerate temp swings well... Suggest you get a "garang" chiller
. Needing to top up often this will result in salinity fluctuation... Not a good thing for clams... Solution : Get an auto top up...for accurate daily top up...
. AS you mentioned the set up is in blacony, rain might easily get in Solution : Get clear palstic/glass to prevent the water from coming in...
If you can overcome the abovementioned problems you might well be on the way to have a first clam farm in singapore....