low alkalinity or surface water tension? Help

[Spaghetti]

I have an acraylic 55 gal. fish only tank that is a year old. I have both crushed coral and sand as a substrait, live rock (about 1/3 of the tank), 2 powerheads, a protein skimmer, and an external canister filter (i.e., magnum). Over the last month, I've had been adding buffer because of low ph 7.8/7.9 and have been told that there may be a build-up of carbon dioxide (due to excessive surface water tension). During this time I've also noticed that my canister filter has bubbles at the top of the canister that are being pushed out of the exit tube into the tank. I have no idea why this is happening.

The local store guy recommended that I address the surface water tension by putting an air pump with a airstone in the tank. I used the pump for a week or so, but didn't like the results (seemed artificial in the tank and casued a mess on the inside of the top of my cabinet). He then said I could try re-arrange the direction of 1 of the powerheads so that it causes a "ripple" on the surface.

Also, why would the surface water tension issue take a year to show-up? Shouldn't it have been an issue sooner? The store owner said that if the build-up of CO2 is casued by surface water tension that adding buffer will not help.

In the past I've only done water changes every two weeks and will now start wkly changes (5% changes at a time). I am hopeful that this will help.

Do you have any other options/suggestions that might help me? :help: Thanks

 

[Fishieness]

i dont think the LFS employee used the right term when he/she said "surface water tension". but you should have some ripples on the top to prevent buildup of dust/oils and to increase the surface area for gas exchange. but if you have a protein skimmer, you should have adequate oxygen levels.
it is possible though that you are having issues with flow. how many gph do you have in your 55?
also, what salt are you using? that could be the cause of the low ALK. and waht is your ALK? all you mentioned was your pH.

 

[Spaghetti]

Thank you for the help. The 2 powerheads are 145 gal/hour each, and the magnum is a 330 gph. I don't know how much flow goes through the Protein skimmer (it's a red sea prizm skimmer). I'm using Oceanic sea salt mix (BTW I purchased a large quanity and now the LFS says they don't carry it any more as they don't think it's all that great). I'm sorry, but I don't have a kit so I can't telll you the ALk at this time. I am going back to the store today and will get a kit. Thanks again.

 

[dorkfish]

Leave some water out of the tank for 24 hours then test it for PH. If it is CO2 building up that is cuasing the low PH, you will see a higher PH on that water than you would see on water just taken from the tank. If it is not any higher than the water just taken from the tank, then alk./calcium is your cause.

But, besides the point, a PH of 7.8/9 has proven to be fine IME/IMO for keeping a softy reef.

 

[Spaghetti]

That's a great idea re: the testing of water taken from different times. I'll give it a shot. Thanks.