pH, new rock, dinos...

bsfmaximus · Sep 17, 2017

About a month ago I sold about 10 pounds of live rock that was covered in button polyps. I replaced during aquarium adventure's big sale within 24 hours with a big piece of their liverock. I'm wondering if it wasn't fully cycled yet...
My nitrate levels have been higher. 5-10ppm versus 0-5 previously. I've been fighting dinos and some algae on that piece of rock only. Today I tested pH and it was 7.75. It is usually 8-8.1. I've also had a upcreep of diatoms.
My tank is 54 gallons, no sump. I've got about 45 pounds of liverock.
Is it reasonable to assume that particular piece of live rock has been cycling and the source of these issues? Any advice?

Randy Holmes-Farley · Sep 17, 2017

Can you see visibly dead stuff on the rock? If not, I doubt it is the source of the nitrate or the pH lowering.

Without seeing anything on it, it might have phosphate bound to it, which can encourage local growth of algae , or it might just be new open territory for algae to conquer that isn't already occupied by other organisms.

pH is controlled by CO2 and alkalinity. If alkalinity is normal, the pH can only be low if the CO2 in the water increased, which might happen if, for example, you closed windows in your home for some reason. Or it might be testing error, requiring recalibration.

bsfmaximus · Sep 17, 2017

Thanks, Randy... not sure if they'd leach into the water but phosphates are measuring 0. pH monitor has been double checked and calibrated. I see what appears to be green hair algae in the same place I experienced dinos. Here's a pic of the rock, notice only part of it is dark and that is where the dinos have grown. The second pic is the green hair algae or what I assume is. Where it exists are all places I had sucked up and blown off dinos.