ph drop after large water change?

S

sCeRaXn

AC Members
May 29, 2009
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I did a 40% water change in the 55 on saturday, and since then the ph has steadily dropped. It dropped to 6.0 and finally settled at 6.4 last night and has held there all day. It usually stays at 7.0-7.2 no matter how big of a water change you do. I started dosing with Excel on saturday as well. I thought it might drop a little, but not a whole point. The fish and plants seem unaffected by the drop, but they are all fairly hardy fish. Normally i wouldnt stress it too bad since the occupants are fine, but im about to go pressurized c02 in a week or so and im scared itll drop the ph to extremely dangerous levels. What should i do to get the ph back up? Should i just wait it out and see if it starts coming back up on its own?

Heres the specs

Tank:
55gal
1.5-1.7wpg cfl lighting(good reflectors)
Rena xp2 and Top Fin 60 filtration
Powersweep powerhead
Natural Gravel substrate
Dosing Flourish twice weekly and Excel daily by their instructions

Fish:
Juvenile Pacu(8" and fat as hell)
Juvenile High Fin Pleco
7 BA Tetra
3 tiny Clown Loaches
2 Large Black Apple Snails

Plants:
Amazonian Sword
Huge Melon Sword
Argentenan Sword
5 small Corkscrew Vals
2 Anubias(they hate Excel)
Rotala
1 unknown(maybe moneywort?)

Sorry i dont know all the scientific names, thats way too much to look up right now lol Any and all help is appreciated!
 
Anybody? I know its a long post, but i tried to give all the necessary info the first time around so people wouldnt have to keep asking what my setup was.
 
What are you using to test the pH?
Have you tested KH?

Your pH might be lower because the new water is saturated with Co2 which is acidic. Once it gasses off your pH will rise again.

To test, let your source water sit out overnight. Measure the before and after pH.
 
get a test for kH.
but CO2 causes a drop in the pH as it helps create carbonic acid.
you may also want to test gh

this link helps explain the drop in pH when adding CO2

http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

in essence tho the effect on the fish is small as long as the CO2 level does rise to high.

i suspect it could be possible the excel that is causing the swing.(CO2 will cause a swing too)
 
but it could be adding or creating another acid.

the stuff is known to kill hair algae as well as some vals.
no telling what it could do... ;)
 
Im using an API drop checker. It was sorta old so i went and got another one yesterday morning and it read the same as the old one. Ill have to order something to test the kh because i cant find anything locally. Star_Rider- I actually came across that link while researching c02 the other day and it helped alot. What you said about the carbonic acid makes sense, but its never happened before. Its city water though, so you never know whats in it lol It read 6.6 this morning so hopefully its coming back up. I just took a sample and im letting it sit out for a while before i test it again. Thanks for all the help
 
I hope Excel doesnt kill my Corkscrew Vals. They seem to love it so far, but my Anubias did at first too and now theyre almost completely melted.

When i get my c02 up and running should i quit dosing Excel all together or just lessen the amount? From what ive read its supposed to increase the plants rate of absorption of c02...but ive read other threads that say you should only use it to battle hard to kill algae if youre using c02.
 
yes if you are adding CO2 you don't need the excel

city water can be 'spiked' in some areas where there is acidic water they buffer it a bit to slow corrosion. other placed CO2 may be spikes and will gas off after a bit.
that is why it is suggested to try setting a sample of your water out overnite.. add an airstone to aggitate to help gas off.
then test.
if there is added CO2 in the water the pH should start rising ot will stabilize after it sits out over night.
 
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