Drastic drop of pH levels within a few hours?

Question

Yesterday I cleaned my tank (removed 15% of the water, vaccumed the gravel) and replaced the water with treated water (and Bullseye 7.0 since the tanks water was at about 7.0) after about 6-7 hours later I checked all the levels of ammonia, pH, nitrate, etc. Everything was okay. The pH was at about 7.1. Today, I checked the pH and such again, and everything was good. Suddenly, about 20minutes ago, all my fish darted to the surface and seem to be gasping for air, and the pH dropped to an astounding 6.0. What would cause this huge change of pH levels, and what is this pH doing to my fish, and the water?

Well, it's a 35 gallon tank. And I have tested the pH level of my tap water, and its extremely high, like 7.8+. And also, on top of my tank being horrbily cloudy, if you look up from underneath the tank, the top of the water appears to have white specs all over it like someone sprinkled grated cheese on it (lots of grated cheese). I've managed to bring up the pH to 6.6, but I don't think I will try to bring it up anymore because I don't want to but them under any more stress. What else should I do, and what is the white specs?

Answer 1

This can be caused by several different things however, seen as you did a water change prior to the event the most likely scenario is that your natural water table is acidic and your water company uses a buffer to make it more palatable so raising the pH from 6 to 7 for your consumption, needless to say at some stage the buffer has broken down in your tank and you've had a crash.
Its not disastrous at this stage but it can and often does wipe the fish tank out.
The only way to avoid this is to store the water your going to use for at least 24hrs so the buffer breaks down before you use it, then use it. Or use an RO (reverse osmosis) system to provide your own water remembering to add salts back into the water to replace all the beneficial minerals that have been removed.
Your fish have survived thus far, some ppl will tell you to start trying to rebalance the pH however, all you will do is stress the fish further, doing a water change is more likely to cause the same problem tomorrow.
The fact that your fish are gasping at the surface is unusual, they tend to sink to the bottom once acidosis occurs, so maybe its not so bad i would buy another pH test kit and test the results against each other, just in case.
Find a Ph buffer your LFS should have something that will work and add that too you water when doing water changes or if you get consistent tests from your tap water once its settled for 24hrs then steer your type of fish to that type of water.
Another one I've come across again relates to your water supplier, during the spring and during the autumn they send chemicals through there systems, the idea is get rid of all the inverts and other things they dont want in the system, This one when they do it is unpredicatable and devestating. Result is similar however the chemicals they use break down any buffer you put in and obviously are designed to kill shrimps and other water crusteaceans.

Answer 2

Usually you don't have to worry about the pH level because the fish you buy at the store are born/raised in those types of conditions. The fish that are caught wild, like ones that are very difficult to breed in captivity are the ones where you have to worry about the pH level. Adding more chemicals usually makes it worse because it will have the pH fluctuate which is much worse than it being stable at a 7.8 And the pH level wouldn't kill the fish that quickly. I am more worried about your ammonia, nitrite, and nitrate levels. If you haven't cycled the tank then this is the problem. Have you cycled your tank? How long as the tank been set up?

Answer 3

Basically the buffering capacity of the tank got over loaded. It's commonly called pH bounce and is one of the biggest hazards to adjusting pH. Without knowing the carbonate hardness and the pH of your tap water it's impossible to say how low it might drop or if it might even bounce back in the other direction. If you would like to add that information to your questions, along with tank size and the fish you keep or email me that info I can help you figure out what steps to take.

MM

Answer 4

for fresh water tanks you can buy pH up and pH down drops at your local pet store.
I have never tried them and dont know how great they work or if they will stress the fish.
If the white spots look like the fish is covered in sand you might have ich.

Answer 5

This is a very rare case. I think some how something got in there and changed the pH level.