plants respiring?

[crazycat]

ok--plant newbie here (madasafish don't laugh!)

so here's the deal:

ammonia: 0
nitrite: 0
nitrate: 12.5
ph: 7.0
kh: 3dh (just added crushed coral to the filter to try to raise it)
phosphate: 1 (i think but i seem to have a faulty test)
lighting: 3wpg
filtration: fluval 404 and 304
pressurized co2 system
dosing with potassium after water changes and 2x during the week (according to the fab article by malkore) and with csm+b and iron (not with extra nitrate yet until i can figure out my plants' uptake)

and now for my question:
i've been noticing bubbles coming off of my plants, espcially off the ludwigia repens and another delicate plant (name unknown)--bigger bibbles from the ludwigia, and smaller bubbles from the other

is this "pearling"
are my plants really releasing oxygen?

or is there some other thing having to do with bubbles coming from plants that is bad, bad, bad?

in other words, have i actually managed to create a hospitable environment for my fish AND plants???

 

[malkore]

yes, bubbles on the leaves are oxygen, which cannot dissolve into the water because the water has become oxygen saturated.
they should occasionally rise from the leaves to the surface.
CO2 is actually low, only 9ppm with the Kh and pH you've given. I would increase it a bit, and your plants will really take off.

 

[crazycat]

thanks malkore! how many ppm should i increase my co2 to?

 

[malkore]

at least 20ppm. 35ppm is about all the higher you need to go, but its best to work your fish up towards that.

also, since you're at the lower end of a good Kh, I'd probably say no more than 30ppm, just to keep pH more stable between day and night.

 

[crazycat]

thanks again malkore!

i'm slowly lowering my ph to increase the co2 levels--i don't want to shock my poor fish too much--it's still a new tank (about a month old) and can easily become unstable. it's also carrying a fairly large bioload given its age (although i used filter media, substrate, and water from established tanks--so it's pretty much cycled--and i'm doing water changes every other day so far). i've added crushed coral to one of my filters to try to raise the kh--it's only been 2 days, so i haven't seen a measurable increase.

how long do you think it will take to see the kh come up, and is one fluval basket of crushed coral enough to raise the kh on a 125g tank?