Re: Enigma, bubbles during water changes

From: "CORBEIL, SCOTT" <corbels at macmail_mcgawpark.baxter.com>
> Subject: Enigma
> I have a 150 gal. heavily planted tank, fertilized with CO2 and PMDD. 
> Nitrates are 5-6 ppm, Fe is 0.5 mg/ml, GH =3D 120-130 ppm, Ph is 6.4-6.6,
> phosphate level is below 0.1ppm.  The weird thing is every time I do a
> water change I suddenly see a burst of activity in my plants, i.e. the
> plants release oxygen bubbles like crazy.  This, to me, indicates a
> nutrient deficiency but I can't figure out what it could be.   Any
> idea's???

Paul Krombholz wrote:

> This has been reported before, and there was a long discussion about a year
> ago.  If the new water comes right out of the tap, it may be supersaturated
> with dissolved gasses, having been under pressure.  These gasses may come
> out of solution on the plants, or they may even diffuse out of the
> supersaturated solution into the air channels in the plants and make it
> look like they (the plants) are making more oxygen than they are.  Tell us,
> Does the new water come out of the tap?  If it does, try storing it for a
> few days and then adding it.  After a few days of storage, the dissolved
> gasses should be in equilibrium with the atmosphere, and any additional
> bubble production after adding the stored water could only be due to either
> some additional CO2 in the stored water or some nutrient that the plants
> were deficient in.

This very same bubbling occurs in all 3 of our plant tanks every time we
do a water change - new water is 100% DI reconstituted and stored for 1
- 3 days before use.

Since our water mix is so soft, 3 GH & 3 KH, I thought that it might be
calcium that was limiting so I started experimenting with adding small
amounts of CaCO3 to 1 of the tanks with no change noted except a 1
degree rise in KH - no change in GH or PH - which puzzles me as I
thought that when adding CaC03 both KH & GH would rise equally?

However I've also started adding PMDD for 1 week now to all 3 & just
today in 1 of the 3 tanks (not the CaC03 test tank) the bubbling started
like crazy just like it does after a water change - so I'm assuming its
something in the PMDD, although I don't know which nutrient it is.

Rebecca Marsh
in currently rainy Gold Bar, Washington where the tap water changes
almost as fast as the weather