BBA Outbreak

Only thing I see is that a pH controller might be contributing to an unsteady CO2 level. Maybe take it off and see if things get better? Unless you're really blasting the CO2, I don't think your fish or shrimp will be harmed

For short-term treatment, you could try ODing or spot treating with Excel

Having a controller can just add one more thing to muck up the works. All depends if the probe is calibrated and how it's been set up to work... As stated the drop checker is saying your in the clear but have you tried to bump it up a little more?

Unfortunately it's a little late as your in the middle of you outbreak.

Use Excel as a spot treatment if you don't want to rip everything out and scrub it down. The nice thing about the spot treatment is keeping your scape intact. Some plants don't like excel but I have yet to have one melt because of it.

Keeping a steady low bubble count is how I've been using mine. One day I'll complicate my life with a controller. Just not yet.

The controller, probe and drop checker are lying to you, the BBA says you have poor C02. Period.

What controller are you using?

Just a thought, if its the SMS122, you are *ONLY* supposed to calibrate with the 7.01 solution and *NOT* the 4.01 solution (search around if you don't believe me), not sure that's the one you are using, but for our purposes I think it will distort the pH readings...

Also, per this link, it might be a nutrient deficiency, but that's hard to imagine w/ the EI?:
http://www.theplantedtank.co.uk/algae.htm