Hopefully someone can help me here :-)

Recently I moved house and was forced to rebuild my 55 gal (48"x20"x14")
tank from scratch. It's a community tank, which until I moved had very
happy plants which were often pearling streams of bubbles during the day
when the lights were on.

Since moving, the plants are decidedly unhappy and there is some algae
growth (but not too bad) on leaves.

Lighting is flourescent - 1 x 36W 7500K + 1 x 36W 50/50 6000K/Actinic. On
around 10 hours a day.

Tank chemistry at the moment is as follows:

pH 7.2
kH 1-2 deg
Nitrate: 20ppm
PO4: Unknown

From the pH and kH I believe the dissolved CO2 is probably around 2.8ppm
which seems very low.

Problem is, if I attempt to increase the kH, the pH follows it, so I'm
unable to increase kH to increase CO2 concentration. I've never needed to
add CO2 with a reactor before, so there must be something else I missing.

The tank is dosed with Sera Florena fertilizer every couple of weeks.

Anyone have any suggestions about how I may improve the water chemistry to
get the plants in action again?

The fish are all perfectly happy BTW.


Thanks
Graham.