ph and water

[sparkle]

Hi All, I am loosing fish...heres the problem
very very soft water
very very high alkalinity
ph around 8.9-9.0
125 gal tank freshwater
Filled tank 2 months ago from tap water, with softened water. My water softner runs thru the whole house. Used a De-ionizer filter. I want to have angels and tetra's in this tank. All tetra's die in it after a week or two. I have used 7.0 nuetrilizer And 2 jars of Discus buffer over a week period. After 3-4 days the water bounces back up. Even with the buffer it only went down to 7.0 but all is back to what it was. It did not stabilize! Can anyone help? There is no organic material in the tank.

[sparkle]

ooPS FORGOT TO SAY I AM RUNNING 2 MAGNUM 350'S AND 2 BIO WHEELS AND A BUBBLE WAND...

[FinAddict]

What do you have in the tank. Type of Gravel or decorations ect.?

[sparkle]

HI I HAVE GREEN GRAVEL. JUST YOUR PETSHOP REGULAR STUFF...MY HUSBAND PICKED IT OUT. YUCKY! MANY PLASTIC PLANTS AND THINGS THAT LOOK LIKE ROCKS BUT ARE NOT REAL. THEY ARE VERY PRETTY BUT NOTHING ORGANIC...I WANT TO ADD REAL PLANTS LATER WHEN TANK HAS BEEN UP FOR ABOUT 4-6 MONTHS. I HAVE ANGELS AND TETRA'S. LONG FIN BLACK TETRA'S ARE THE ONLY THING THAT HAS LIVED SO FAR WITH A COUPLE OF CORY CATS. A LOACH AND A SHARK. ANGELS DIE OFF A COUPLE A WEEKS....SMALLER TETRAS JUST GO AND FADE AWAY. I CAN BE WATCHING TV AND THEY ARE FINE A COUPLE OF HOURS LATER ONE WILL BE FLOATING AT THE TOP??? I AM CONFUSED. NEVER HAD WELL WATER BEFOR WITH TANKS.