Very Confused With Ph!

[stanicol]

Hello all, I'm totally confused...

I have a 300ltr tank that i has just completed a fishless cycle, we won't be adding any fish until next weekend so i am topping up the ammonia to 4ppm daily.

I just did (as a bit of an experiment) a 20% water change to see what would happen to the Nitrate level and the pH.
The Nitrate level did come down a bit as expected but the pH has jumped from 7.2 pre water change to about 8.2/8.4 after. I thought the tap water pH must have been very high but it was only 7.8.

I am using API liquid tests and I have double checked the results, they seem to be correct.

I did add the ammonia to 4ppm after the change but before I tested the pH and I used API Stress Coat to dechlorinate.

The tank did have 5 teaspoons of baking soda added about 2 weeks ago to increase the kH after a pH crash!

Can anyone explain why the pH has jumped above the pH of the tap water I added?

If this happens with fish in the tank it wouldn't be good for them i assume?

Thanks Stan

 

[P&J]

I did add the ammonia to 4ppm after the change but before I tested the pH and I used API Stress Coat to dechlorinate.

Someone with a bit more expertise might want to chime in, but I believe the ammonia will raise your pH. This is why some people say to not bother checking the pH during a fishless cycle, because the ammonia will throw it all off. (I just check to make sure it doesn't crash too low!)

-P

 

[LauraFrog]

Ammonia is a base - did you add the ammonia immediately before testing the pH? You should not add ammonia to the tank for two days before you add fish. Then test right before you add them and if the pH is still so high, you should take several hours acclimatising them to make sure they get used to it slowly as any pH over 8 is considered very high - probably too high - for general tropical keeping. It's true though that ammonia can send your pH up.

Baking soda won't do anything for your kH, it will only increase your pH. If you want to increase the kH, you should use crushed coral, limestone chips, or commercial oxy blocks. If your pH is really high and you're increasing your hardness, I recommend that you stick with hardwater tolerant fish - most catfish including plecs and corys will accept these conditions, and also livebearers and rainbowfish. Tetras and rasboras do not like a high pH at all and so you would be best to stay away from those if your pH is always going to be high.

Test right before you add ammonia tomorrow and post the new results. If it's still way up, there might be something else interfering with the pH. If there is, it's best to find it before there are fish in the tank.

 

[waterdrop]

Sometimes, trying to predict what the water chemistry patterns of your stocked tank will be like by observing what's going on during fishless cycling can be an exercise in confusion. In my opinion its just better to think of water during fishless cycling as a completely different thing, a special soup for growing bacteria. After stocking, you have a new situation with your water and there will be not much alternative but to just get used to once its ongoing.

I would have a slightly different description of baking soda. It causes an immediate and strong addition to the carbonate hardness of water, so the KH should increase sharply when it is added. The increase in KH will result in a resulting addition to pH, up to a point and depending on the pH starting point. But baking soda's effect does not last long and it is a very poor choice for altering KH/pH when you have fish, precisely because of the quick fluctuations associated with its use.

In contrast, crushed coral is usually seen as the method of choice when one has decided that KH/pH must be raised by artificial means (a choice that should be resisted as much as possible unless one has clear reasons.) Crushed coral will be very slow and steady in delivering the same upward movement of KH/pH.

A couple of other comments: at the end of fishless cycling it should be fine to introduce fish the same day or next day after the tank has had ammonia, as long as you do indeed perform the 90% water change recommended in rdd's pinned article. By the time the big switch to fish is made, the filter should have already proven itself by performing at least a week of dropping ammonia and nitrite from 5ppm to zero ppm and thus it should easily dispense with any leftover toxins prior to fish introduction. The bacterial colonies will also be robust enough to handle a couple of days without ammonia if that happens, but beyond 2 days, you wouldn't want to allow your colonies to be retracting due to lack of ammonia.

Anyway, bottom line I just wouldn't stress on trying to understand your future KH/pH patterns based on the unusual things you will observe during fishless cycling.

~~waterdrop~~

 

[stanicol]

Hi again, I have just done the tests again and the pH has dropped to a more sensible 7.6ish, must have been the ammonia that increased it last night as you guys thought.
Just a small question, if I found that I needed to increase kH without wanting to increase the pH, would this be possible and if so, how is it done?
Thanks

 

[waterdrop]

The method of choice.. the thing you should be hoping will work I believe.. is to raise KH via your tap water. Often, even with very soft tap water, there will be enough dissolved salts that constitute carbonate hardness that they will be higher then what your tank reads after a week of plants and bacteria using them up. The weekly water change will thus constitute a raising of the KH without much, if any, raising of the pH.

Perhaps you have a good liquid KH test. If not, pick up one like the Tetratec KH test kit or the API GH/KH test kit and start getting a feel for both the pattern of KH coming from your water authority and for the pattern your tank is doing.

If that's not enough then I suppose the next step up in strenght of action is going to be trying a very small amount of crushed coral (like a tablespoon) in a bag in your filter, but this may still carry the possibility of raising pH by a little eventually, after its raised KH.

~~waterdrop~~