"Alex R" wrote in message
news:uVMma.484026$S_4.541144@rwcrnsc53...
"linda mar" wrote in message
...

If you're going to add medications to a planted tank, be aware that most
medications have negative effects on plants. I never add any medications
to
my tank. I guess it depends on what's more important to you, fish or
plants.

at this point, probably the fish... I know plants are living too, but...
(not to mention I dont' have the best setup for the plants, so my
expectation for my plants' longterm survival is rather low) but like I said,
I'm trying to search all venues before resorting to medication... and if I
can treat individual fish in the quarantine tank, I would, but whatever is
affecting my fish seems contagious to a certain extent.. so if I do
medicate, it will have to be the whole main tank. (which is why I'm a bit
nervous about just blindly doing this)

so I've started to test pH more regularly (every day for the past 4
days).
it's a moderately planted 37G tank, nitrite, ammonia, nitrate is always
zero... temp ~75F.. UGF (2 aquaclear201 powerheadss) + HOT Magnum.

You should probably add some nitrate to help the plants.

yes.. but at this point, I really don't want to add anything until I figure
what is going on with the fish population...

My guess is that you're not putting the test tube directly against the
color
chart card when comparing. If there reflected light coming from behind the

no.. I have the tube right up against the paper. I read it in sunlight (or
very bright halogen light), and when in doubt, I always create the control
specimen, which is measuring the pH of my tap which is really high in pH.
there is a marked color darkness difference between very high pH (using tap
water), which does reflect the 7.6 color on the chart. but what i get is
from the tank is a pale version of the 7.6 (sort of like a 30%dilution...).
I guess it may mean somewhere between 7.2 and 7.6..???

test tube, the color will look washed out and your interpretation will
likely be inaccurate. I have used the AP kit before, and I believe I
stopped
using it because the printed colors and the test tube solution colors
didn't
match well, and there are gaps between 6.0 and 6.4 and between 7.2 and
7.6.
The Hagen kit works a little better, but the AP one is still pretty
usable.

may be I'll try the hagen pH kit... AP is a bit annoying for me since my pH
does seem to land smack-in-between where they break the pH brackets...

If the KH remained the same, then I believe the pH increase you're seeing
is
actually a daily cycle. In the daytime, the plants probably lower the CO2
to
below equilibrium, causing a rise in the pH. Then at night it builds up
again. In that case, you should increase the surface agitation to let the
atmospheric CO2 diffuse into the water better. Without CO2 injection, the
more surface agitation, the better.

How wide can the plant-respiration-induced pH fluctuation be? can it really
go from 7.0 to 7.6? (37G, moderately planted...)

the surface is quite agitated, and water very well circulated.. I suppose I
can try adding more agitation (both Aquaclear 201 powerhead outputs are
directed directly towards the surface, as well as the HOT Magnum output.
there is a tremendous amount of surface ripple caused by total of about 400
gph water being spurted towards the surface (enough to suck down some air
into the tank where the different current meet.. sort of like a mini vortex
going on...), so... (lots of current in the tank...). may be I should
switch the HOT Magnum to trickle-type power filter? would that give more
gas exchange due to cascading water? (lower flow rate than the HOT Magnum,
though)

You mean the GH drifted from 6 to 2? A drop in GH is usually caused by
snails. When they grow, their shells gather up the calcium from the water.
So a GH drop is due to growing snails and a KH drop is usually due to
nitrification activity.

no. GH went *up* from 2 to 6... and no.. I have no rocks or any
mineral-creating stones in the tank (just some bogwood and the standard
inert aquarium gravel). There has been some explosion of snail population
which makes sense (higher GH supporting more snail shells..).. but I don't
think I have done anything purposefully to increase GH that I know of (other
than potentially the tap water had a very high GH one weekend or something),
unless those seachem flourish, flourish excel, flourish iron adds to GH (I
e-mailed them and they said it should not affect it)

Increasing the KH in your tank will not stabilize your pH. However, I
would
still add some baking soda to make it 3 or 4 degrees, just to be safe from
the KH completely diminishing. To help with the pH fluctuations, increase
surface agitation.

wouldn't adding baking soda increase the pH of the water? if the water is
already at or close to 7.6, I don't think it's such a good idea to increase
pH further (esp for the fish)... are there other means to increase KH
without increasing pH?

linda
__
Alex R