Ok so i look at my 110gallon tank today and go.. "hrmm that looks a bit cloudy, wonder why?" So i took out my trusty test kit and checked everything. Ammonia 0, NitrAte 0-5, NitrIte 0.25 and the pH is 6.6!!! Never since having test kits have i had a pH this low.

My tap water is 7.8, my greenwater (well its not green anymore ) tub is around 8. All other params in the other tanks are the same as the 110g. I did a 25% weekly water change yesterday and sucked my red caps eye out *cries*, so i've added melafix for the past 2 days, he seems to be ok, just with a huge hole on the side of his head. But melafix wouldn't cause a pH drop right?

I dont want to do another water change because that will just shock them more by raising the pH. Will it come back to normal by itself? But how did this happen in the first place... Does the pH of tap water change day by day? Because i didn't test it yesterday, I only noticed the tank a little cloudy today.

Bad news on the pH.

I have the same problem in Hong Kong with the pH is all over the place.

I just buffer it to something really high, like pH 8.2 and KH 160 with baking soda so there is no chance of it dropping down between water changes.

Slugger

The nitrogen cycle itself will produce nitric acid (nitrate) - that is an acid - which can lower your pH if you do not have enough kH or buffering in the tank. You do not say what your kH is - but if it is very low, even a little bit of extra food, rotting wood, left over mulm, etc. can cause the pH to drop.

You should find out what the kH of your water is, and, if it is low, supplement it to raise the kH - baking soda being the easiest and one of the safer methods used.

The buffer from the kH will help absorb any pH changes, holding the pH stable for you even in the presence of great amounts of nitrate, etc.

It will not come back by itself. I would do multiple smaller water changes to bring it back up. Careful buffering will stop this from happening again.

Your poor little red cap..... I hope he feels better soon.

I dont have kH test, but my water has never done this before. Its starting to come back up on its own though, the water is clear again. Theres NO chance of leftover food with my little piggies! It didn't go down any lower with is good though.

I just had a similar problem with my PH dropping. It had been steady at 7 for the past 9 months+, but for some reason, the PH out of my tap has dropped from about 8 to 7, and the ph in my tank dropped to 6 I know I have very low KH, but I do have crushed coral in my filter (have for a year now) but the PH is still very low even after daily 30% water changes. I am using proper PH 7.5, and that is barely keeping it at 6.8.

This topic is neat since I was reading the FancyGoldfish Book again last nite and found some interesting things about Ph Drops..

1. More O2 in the tank the more stable the Ph wil be.
2. The higher the Carbon Dioxide (which plants and over loaded fish tanks cause) will lower the Ph level in the tank.
3. More circulation of the tank will help raise up the Ph level....