Like everyone else, I wouldn't put that in your DT. Either get a stronger light or do what Nano-newb did. Another thing to consider is that it is very easy to scrape the black off the back of the Biocube. I have done it and it was not hard at all. That way you could see back there and you could put a light up against the glass in the back for more lighting to your fuge.
Really though, I think the bottom line is you have to do more water changes. You can try this and that but there is no substitute for proper tank husbandry and that would include 10% (3 gallon) water changes weekly. If your nitrates are high than I would do 10% everyday until it was at an acceptable level(under 20.) HTH