My pH suddenly at 7.8...is this why?

[iwishtofish]

I just started using RO/DI and rinsing my frozen food. I think a lot of my algae might be dying because of reduced phosphates from this.

Now my pH is down and there are lots of bubbles forming on my rocks and sand, mostly where the algae is. Is it possible that these bubbles are CO2 being released by the dying algae, and that this CO2 might be partly responsible for my dropping pH?

The bubbles:

http://i211.photobucket.com/albums/bb113/bjdoyle64/bubbles2.jpg

http://i211.photobucket.com/albums/bb113/bjdoyle64/bubbles1.jpg

[bertoni]

The bubbles are oxygen, most likely, produced by photosynthesis. The last picture shows some microbial pest of some sort.

[iwishtofish]

bertoni, do you mean a microbial pest such as cyanobacteria?

[bertoni]

Yep, that's one possibility.

[stevensun]

agree with bertoni. It looks like cyano to me too.

[iwishtofish]

Thank you both...it's really strange, because it is in just this one place on the rock, and actually has some brown algae-like strands coming out of it. (The photo is a cropped macro, and doesn't really show this well).

Maybe either cyano on top of algae, or just dying algae. Either way, I'd like to see it gone! :)

[tmz]

CO2 may be the culprit but not from the algae/rinsed food scenario. Is it possible you have less air exchange than usual or is the room where the tank is subject to higher CO2 at this time of year? Are you using a Calcium reactor?Cyanobacteria would produce the oxygen bubbles and would thrive on higher than usual CO2.

FYI In the November issue of CORAL magazine there is a summary of a study done on frozen foods which showed that even when continuously frozen most contained vibrio bacteria which could be harmfullto fish. The recommendation was to rinse with regular chlorinated tap water which would remove the packing water nurients and it is hoped kill any pathogens in the food.

[iwishtofish]

tmz, I live in a small apartment on a noisy roadway - it is quiet until I open a window or door. So, yes, poor access to fresh air may be contributing to my problem. No calcium reactor, or dosing of buffers or alkalinity at this time. That may change very soon.

Thanks for the frozen food heads-up. Was that article published online? I'll have to look for it!

[bertoni]

It's unlikely that changing the CO₂ level will change the growth rate of the pest. There's plenty of CO₂ even with outdoor aeration. The pH would have to be very high before it could be an issue.