My tank is actually at 6.4-6.6.
The water from my tap is at a pH of 8. I figure between the fluvial stratum, spider wood, and plants and snails the pH has been lowered significantly to where it is in the tank of 6.4-6.6. I've, since yesterday, learned this can lead to old tank syndrome and the possibility of ammonium changing to an ammonia spike if the pH goes up, say during a water change. I'm going to try a ten percent water change this evening and see where my pH sits after that before I decide to make any other additions of chemicals or additives.
As far as sunlight hitting the tank, this is less of an issue. I used a light monitor meant for gardens and faced it towards the window for a day and got a heavy shade readout. The window faces the NE so there is very little direct sunlight, plus we keep the blinds half way closed.
Wen I do add fish I will likely start with either some Otos, Cory's, bristlenose plecos or possibly hillstream loaches. I'll have to see where my pH lands before deciding. From there I'm thinking of zebria danios, maybe some cherry barbs or diamond tetras and a centerpiece fish which I've not decided on. Thinking rainbow fish or a gourami.