high ph?

[Yellowfin]

I have recently switched from salt water to fresh water. I can't seem to get the ph to the proper levels. Even with ph down chemicals the ph climbs right back up to 8.4-8.6. I have done many water changes adding ph down chemicals only to have it clims back up immeditaley. Could it be that the gravel bed is made from crushed coral even though it is more that ten years old? Please help. Thanks.

 

[hollywoodH]

what fish do you have in there matey?

 

[StiX]

The crushed coral is most probably the cause!, the only way it to remover it all and replace with normal gravel or sand. Also do u have any other rocks in there?

 

[Yellowfin]

It's a 55 gallon tank with:
2: tiger barbs
2: tin foils
2: cat sharks
2: angle fish

yes, I have some rocks but they are left overs from my saltwater set up. They appear to be some sort of coral derivitive. Any more thoughts would be greatly appreciated. Thanks!
I have to be honest, keeping the swalt water for all those years seemed easier than the frexh water.