yeh, you do pH soil plants.. or at least its better.. best get a tester, when you test soil its best to test the run-off too..

like, say you want a pH of 6.0 (just an example) and your soil run-off when you use water tested to 6.0ph turns out at say, 7.0ph, you need to down the pH of the water to 5.0ph, that way the water will lower the ph of the soil (and run-off) to 6.0ph... thats just common sense tho really

something you might need would be some type of blind... and some wood to box off the window, (if there is one) that way no light gets in or out, and it just looks like youve got the blind drawn if you do it right...

hope that helps