Help-ph Problem

[RUSSELL]

I have a 125 gal tank , upgraded from a 55 gal about two months ago
since the upgrade I can't seem to get my ph to a decent level like 8.0
in the 55 gal I had no problem but in this tank my ph is down to 7.4 / 7.6
I have about 120 lbs of live rock, I have a power head in the middle of tank aimed up creating waves and I have power heads on each side of tank aiming towards the bottom
I have live sand for the bottom of tank, all fish no corals
I've heard everything from glass tops nop good for tank or maybe carbon dioxide problem
Today I added some kent ph buffer ,any ideas what could be the problem

[Samper]

What else are you adding to the tank?

[patsfan1130]

What else are you adding to the tank?

How often are you doing water changes? how long is your photo period?

[RUSSELL]

[THATS IT JUST PH BUFFER ,BY THE WAY IT CAME UP WHICH IS GOOD, i WILL HAVE TO KEEP AN EYE ON IT QUOTE=Samper]What else are you adding to the tank?[/QUOTE]

[RUSSELL]

I do water changes once a week, change 10 gal a week, this week I did not get a chance to do it with the hurrican

How often are you doing water changes? how long is your photo period?

[Meric]

The bottom line is something either being added or by natural causes is creating acids in your tank which in turn lowers your PH.

Some culprits are:

RO/DI water can sometimes have a very low PH, mine is 5.5 out of the unit. Plus it has no buffering since RO/DI process removed all buffering agents.

What is you current ALK reading in the tank? ALK should be at least 8dkh but 10 to 12dkh would be better. ALK should be under 15dkh.

High bio load (ie: Lots of fish or large messy eaters) can produce a lot of ammonia that can in turn lower your PH.

How many fish do you have in your 55? What kind are they? What else do you have besides fish in the tank? What kind of filtration are you using? Do you have a protein skimmer?

Carbon Dioxide can form carbonic acid in the tank which can lower your PH. This generally happens at night.

Do you have sufficent water movement for gas exchange? When do you take you PH readings? PH is always lowest in the mornings and highest just before you turn off the tank lights. Ph can drop to 7.6 - 7.8 at night.

I always add my make up water after I turn out the lights and I add Kalk (Pickling Lime) to my make up water and let it drip all night. I have to add 1 gallon of make up water every day so I just drip kalk as my makeup water. My PH stays very steady during the day and evening.

I'm not sure if you have checked all these before since your original message does not state the things you have tried or tested. Hopefully one of those suggestions will help.

[RUSSELL]

I have to small triggers-two med tangs-1 tamato clown-one puffer

The eat all the food most of the time, if for some chance they don't I net it out, I don't wait as I watch them and clean tank asap
Im lucky because the power head blows all the fish waster and food to one corner of my tank where I remove it every day
its a 125 gal tank