Yesterday I went ahead and used my 6-month expired Salifert nitrate test kit and obtained a reading of 3 on my tank. So if I can rely on that test kit, that should be fine.
I then took a water sample to Kingfish and John did some tests for me with his D-D phosphate kit. My tank was at 0.015, and the mixed Reefer's Best salt was 0.008. So this tells me that my salt is not phosphate-free, but I'm not very concerned with such a low number. This wouldn't have even showed up on a Salifert kit. The level in my tank of 0.015 is perfect, although John interprets this as being markedly elevated considering the fact that the GHA is clearly consuming phosphates, and therefore without the algae the level would be much higher.
After having the lights off another 3 days and changing the filter socks daily, the algae is receding. While at Kingfish I got another 2 Mexican turbos (that's all that were available) and I picked up a yellow tang. It's small and won't add much bioload, and hopefully it will eat some of the algae. Most of the original Mexican turbos that I got have died for some reason, but they weren't really eating much of the algae if any, so I'm not too disappointed that I've only added 2 more.
As for the welcoming of the yellow tang to the tank, well, it wasn't what I would call uneventful. As soon as it hit the water it was attacked by the achilles tang. The achilles shredded some of the yellow's dorsal fin and didn't let up until I turned off the actinics and provided total darkness to the tank. Fortunately the tail spines aren't yet developed or the yellow would have had some serious flesh wounds. This morning the aggression has mellowed to where the achilles is basically confining the yellow to one side of the tank, not allowing it to venture out. The yellow tang is left to pace only one 30" side of the tank, but at least it's not getting physically attacked any longer. I see this as a positive that the achilles has backed off somewhat, and as long as the stress doesn't overwhelm the yellow I think things will be okay.
To continue the battle against the GHA I'm going to look into running Phosban. I don't think the zeoheads will like this suggestion but it may be necessary as a temporizing measure, and I'll ask about it on the Zeovit forum. BTW, Hop wrote a nice article about GHA in the current edition of
Reefkeeping Magazine if anyone is interested.