No lights, death to organic organisms that meed light. Hence, low pH, high organic wastes (nitrites). It is good that your nitrate are elevated, in that it shows the bacteria needed to turn nitrites to nitrates is present and working. However, things would have definitely worked better with some lighting. It is as near to a fact as you can get that you will have some algae problems with a newly established tank. Algae problems are pretty much the standard with newly established tanks. Cutting the lights at most just moves the time table to a place where the algae comes after the cycling whereby you can use a cleaning crew to help deal with it. Water changes start dealing with the problem before it happens. However, even a few water problems is not going to eliminate all plant nutrients from your tank. That takes time, god husbandmanship, a well functionind bacterialogical system and light loading and thereby light feeding of foods containing nutrients. Plus good water for water changes and top offs. Plus diatom algae (brown algae) is usually a larger problem with tanks that did not use lights during cycling. It is best to use all equipment you have during cycling with the exception of ultra violet filters, which should not be brought on line until a cycle is complete, some people say the same about ozone. If you have them, it is even wise to use carbon ang phosphate remover (ferric oxide) during a tank cycle, as they will remove the phospate and heavy metals leached out of your rock and sand while the pH is low during cycling. Even if you do not plan on using them as routine maintance it is nice to remove them initially.
