Thanks Elaine.

Sorry I didn't give a complete picture so here goes.

Ammonia 0
Nitrites 0
Nitrates 0
GH 140 ml/l
KH 60 ml/l (was 30 ml/l)
current PH 7.3 was about 6.6. I am trying to lower to around 7 but as I add
kh up, up goes the ph as well. ( I am making these changes over a number of
days.)

Aquarium is planted but possibly not as much as it could be....The name of
the plants escape me but does include a broad leaf plant growing out of
wood.. (heard the wood was good for bristlenose). The light is only a
single 2 ft long one. Which I probably should upgrade.

Never had algae probs.
Tank has been operating around 6 months and has always had low KH.
In the beggining I was having trouble with too high a PH. (as this is how
the water comes from my area)

I am wondereing if this shift to acidity is just the natural cycling of this
tank as bacteria in the canister filter grow.
But has got out of hand because of the poor buffering due to low kh.

the med has 4.0mg/ml methylene blue, 2.0mg/ml acriflavine and 0.4 mg/ml
malachite green.

thanks again