Tropical Fish Keeping - Aquarium fish care and resources

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Justinskym51 09-04-2007 03:44 PM

pH low... hmm

I have a 30g tank; currently been cycling for 2 weeks. It has live rock and live sand in it.

Last night, I cleaned my filter and added 1.5g of freshwater to top off the tank from evaporation.

About two hours later, I did a water test and found the pH had dropped to 7.7 every few hrs I tested the water... and it slowly went down to 7.2. It seems to be holding at that pH.

Im going for a reef tank so I've been told that 8.1-8.4 is nominal for pH.

Is the drop in pH to be expected when adding freshwater to top off the tank?
Will it rise back to its original 7.9?
And if it is to be expected then will a drop like that hurt the corals, inverts., and fish that I will eventually have?

I don't use tap water; instead i use RO jugged water which has a pH of 7.1.

My KH is 300ppm. I dont have a GH test.

Any ideas?


jsm11482 09-04-2007 03:49 PM

If the water you added has a lower pH then yes, as the water mixes the pH will drop. Does your tap water (or other water source) have a very low pH? And how much did you add? This seems like a large swing for just topping off the tank.

Justinskym51 09-04-2007 03:54 PM

"added 1.5g of freshwater to top off the tank from evaporation."

"i use RO jugged water which has a pH of 7.1."

jsm11482 09-04-2007 03:58 PM

Sorry, I need to work on my comprehension skills. So the water change is not it then. I don't think I know enough about reef tanks to speculate further. I'm sure some of the s/w members will help out.

Justinskym51 09-04-2007 04:00 PM

okie thanks anyway

caferacermike 09-05-2007 06:32 AM

7.9 is to low for a FOWLR tank much less a reef. Fish only should be at least8.1, if not up to 8.4 PH. It sounds to me like your tank does not have any buffering ability. Your salt mix has a bit of buffer built in. If you have a large tank the ability is thus larger. This has been the debate against nano tanks and beginners since the beginning of time. You can buy extra buffer powder at the shops or you can, as I state all the time, begin adding Kalkwasser to the RO water. You will bring up your ALK, CA, and PH. Your makeup water will read at 12.0 thus possibly raising your PH if added to quickly.

Justinskym51 09-05-2007 11:29 AM

Ok thanks!

I'll look into getting kalkwasser into my replenishing water.

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