Left it alone about 2 weeks and nitrites and nitrates seem to have soared - my test kit said the nitrate levels were toxic! Slime algae all over the glass as well as on the rocks and substrate adjacent to the glass (I think the glass is reflecting the light onto these areas). I just did a 50% water change and dosed some BioDigest. I have also today added a 10W Marina heater since it is starting to get colder.
I also introduced some chaetomorpha about a month ago. It was a mix of two species, Chaetomorpha linum (thin strand) and Chaetomorpha spiralis (thick strand). The C. spiralis mostly died off - part of what caused the nutrient bloom. What is left does not seem to be growing. The C. linum is thriving and growing. Hopefully it can get rid of some of the nutrients and stem the slime algae growth.
In addition, I ordered 10 more opae ula from Pacmed. Unfortunately one (maybe more? since I put the Chaeto in, it has become a lot harder to keep count) died soon after being introduced (had got stuck on the side of the test tube in the post) and was lodged in a place where it was hard to remove. I think this may have also contributed to the nutrient bloom. I believe there are about 15-19 opae ula left right now.