I performed a ~20% water change this past Saturday and noticed that ever since the water has been very cloudy. I was pretty surprised by this because I had also changed the carbon in my filter (and yes I rinsed it first). I decided to test the water today (Monday) and was surprised to see that the pH and Alkalinity were both in the low/undesired range. The other levels were all perfect (Nitrite, Nitrate, and Ammonia).

I've never run into this problem before and was hoping for suggestions. Will another water change fix it? Any other suggestions? I know there are products such as pH Up, but I'd rather avoid chemicals if possible since in my experience they usually do more harm than good.

Tank Specs:
10 Gallon
2 occ. clowns & 1 fire shrimp
no corals
Instant Ocean Salt
Walmart (Great Value) brand bottled drinking water. I've used this water since day one and never run into problems prior to this. Could this be the culprit?

What are your actual pH and alkalinity (and calcium) values? There are times when "low/undesired" ranges are actually based on anything deviating from supposedly ideal or perfect values.

In general if your values are in the ranges listed here, you should do nothing.
http://reefkeeping.com/issues/2004-05/rhf/index.php

Is the drinking water reverse osmosis water? If not, you should use that to limit the nutrients added to the tank.

Also, what test kit brand(s) are you using?

Hi Malcolm, thanks for the reply. Yes, it is RO water even though it's probably not the best quality considering it's the Walmart brand. Unfortunately, I don't have very accurate values since I'm using Jungle Labs test strips. The pH was between 7.0-7.4 and the Alkalinity was between 0-40. I'm pretty strict about doing regular water changes, so I haven't purchased a more accurate test kit in 15+ years. The only reason I even have the test strips is for scenarios like this to get a rough idea if anything is really out of whack.

Do you think doing another water change again so soon would cause more harm than good? I don't have any corals in this tank, but still a drastic change in water quality is actually worse for the fish than just having subpar water.

You should really get reliable test kits if you're concerned about numbers that your test kits are showing. Test strips are very inaccurate. Also, I'm not sure what units you're using for alkalinity. I suggest getting the API test kits.

Even if you are strict about water changes, you will in a sense be groping in the dark if anything happens that a regularly scheduled water change (or something that occurs in between the scheduled changes) cannot alleviate. Test kits, at least the API ones, are inexpensive enough (online stores have great prices) to justify getting them even if you only use them for emergencies.

Water changes can be done as often as you would like.

Also, alkalinity is not really important if you don't have corals.

Also, alkalinity is not really important if you don't have corals.


Could you please explain this for me. I can see calcium levels being "not really important", but alkalinity?

I was a little misleading since coralline algae uses alkalinity. Alkalinity in SW is mainly bicarbonate ions, which (converted in to carbonate) are used to form calcium carbonate skeletons of corals and coralline algae. However, alkalinity is generally more important than pH (which should always be in a relatively large normal range) for coral tanks (mostly stony corals) because bicarbonate is a major influence on pH. Here's some more info on reef aquarium parameters:
http://reefkeeping.com/issues/2004-05/rhf/index.php