A few comments on Dave's concern over bubbles. IMO bubbles are not
required to prove good plant growth. They are neat to see and obvious
evidence of great plant growth but certainly not necessary.
Bubbles indicate high rate of photosynthesis AND a level of gas exceeding
saturation point. Slow growing plants won't tend to bubble although I
have had streams of bubbles coming from the flower of annubias. Most of
my bubbles come from a break in a leaf of water sprite, amazon swords and
a little from val. Less often from hygrophylla and almost never from
crypts. Makes sence when you realize growth = metab. = o2.
With (2) 175 watt MH lamps I get a few bubbles in a 230 gal. (about 1.5
watts/gal). When a third 175 w MH is turned on the bubble production
about tripples. Tells me the water is saturated with o2 and that a
little more o2 has a non-linear increase in bubbles. I would guess that
with more fish consuming the o2 there would be fewer bubbles evident.
To see bubbles all you need do is make a big water change and use water
that is saturated with gas. My well water sometimes comes out cloudy
looking it is so chaged with gas. Until equilibrium is reached the
plants appear to be giving off more o2 - obviously if O2 can't disolve
into the water then it must go off as bubbles.
A downside of awesome growth is a need to frequently weed out and trim to
keep the tank looking good. Also, more likely to get algae on glass. I
admit that now my algae eating fish population is too low but even with a
good stock it is necessary to clean off the glass once a week.
The main advantage I see in having bubbles most of the time is that you
can try things like changing light types or lumens or fertilizers and get
a response in a minute or two. Without the bubbles you don't have a
Bottom line is if the plants are doing good, don't worry about bubbles.
In Dave's case I think the light intensity is a little low to get bubbles
on a regular basis.