aggressive gourami, soft water

Question
QUESTION: I have a 55 gal freshwater aquarium with 2 pearl gouramis(3 or 4 inch), 3 pineapple swordtails, a bala shark (5in), and a four line cat(4 inch). One of the gouramis started out harassing the other, and today i saw it attack the catfish in its hiding place.  It also chases, bumps and nips all the other fish in the tank.  Is there anything I can do to reduce this behavior, or should i remove the fish?  My bala shark does something odd-when the tank light is off and the ceiling light in the room is on, it swims crooked, with its dorsal fin pointing at the light.  IT doesn't matter which way he is swimming in the tank, its dorsal fin points at the light.
Also, my tank is still cycling...we only set it up 3 weeks ago.  I am doing daily water changes to keep the ammonia in the .25mg/l range (it did spike at 1.5), nitrites around .3mg/l (they went to .8), pH has been steady at 7.0.
I checked the hardness when i set the tank up, and the GH was 6, kh was 3.  My test kit said these are within recommended range (just).  Now the kh is reading 1/2 degree of hardness. It said that the ph will be less stable at this level, but doesn't say how to adjust it.  Should i worry about it, or how do i adjust it?
Thanks in advance!

ANSWER: Christine,
You can minimize aggression sometimes by rearrangeing the real estate in the tank, mix up the rocks, decorations etc so that the fish have to restablish territories.
Don;t worry too much about the hardness unless it is excessive.
The PH will vary under normal conditions based on several factors, time of day, amount of photosynthis, C02 concentration etc.
Take the readings 3 times at different intervals add them and divide and get the average PH...as long as you are close to 7 for the most part you will be fine, unless you have PH specific fish, Discus, Africans etc. In that case we will adjust it to fit.
Let me know what the readings are and we will determine if you need to buffer things up some.


---------- FOLLOW-UP ----------

QUESTION: My tanks pH always reads 7.0, I am more concerned with it getting out of whack further down the line, as the pH tends to go down in a closed environment. I only have 2 live plants, an amazon sword and a giant hairgrass.  I also added a piece of mopani wood.  here is a picture link.
http://i251.photobucket.com/albums/gg308/fishingcashgirl/hpim0178.jpg

Answer
Christine,
you can buffer the PH to a degree with any calcium based rock, or shells.
You could add some oyster shells in a nylon pouch to the filter and that would do it, or you can add a couple of clam shells.
Also, you can use limestone rock, ie "reef rock"
That should insure that the PH will remain in the alk. camp.
If you have further questions, just ask