PH crash,HELP!

[I3u11he4d]

My 55 gal. tank crash over the period of 8 hrs.It went from being 7.2 to crashing to 6.0.I turned of my c02 changed 50% of the water and added 1 tlbs of salt for every 5 gals.Does anyone no what I should have done or anything else I can do.Fish really are not happy what so ever and I will be very unhappy if I lose any of them.SO any help would be great.

 

[gomezladdams]

Is the co2 system new Id expect that drop from adding co2.What ph is your tap water?Does the ph of your tap water jump up after sitting out 24hrs?

 

[ewurm]

Did you wait too long to change water?

 

[I3u11he4d]

Is the co2 system new Id expect that drop from adding co2.What ph is your tap water?Does the ph of your tap water jump up after sitting out 24hrs?

c02 has been on for about as long as the tank has been up(2 years).tap water ph is just over 8 after sitting for 24 hrs it drops to 7.2.I condition my water for at least 24 hrs in a 55 gal drum

 

[I3u11he4d]

Did you wait too long to change water?

25% weekly like clock work.The only thing that I can come up with is that the c02 built up from no surface movement.I have been running it with out any kind of filter or pumps for about six months.The only powerhead I had was misting the c02.I just want to know if I did the right things to help or if there are anyother things I could do?