My Ph Levels

[Eebie]

I need some advice regarding my PH levels in my tank.

I do a third of a water change every 2 - 3 weeks and every now and then I notice that my PH levels keep changing and heading towards the acidic end of the scale. I notice this when my fish seem to get a bit skittish.
When I balance the water back towards a more neutral reading, this seems to only last a short few weeks and then starts heading back to acid again.

What is doing this and how can I avoid it in the future? Should I be changing the water more often or less?
My fish are healthy, but there is a lot of black hair algae throughout the tank which I can only keep under control for so long before it starts up again. Is this causing issues also?

 

[SkiFletch]

a few questions for you first

1. do you know the pH of your tapwater?

2. do you know the KH and GH of your water?

2a. if no, where do you live and is your water municipal or well?

3. do you have bogwood in your tank?

4. do you add CO2 to your tank to fertilize plants?

5. what kind of test kit do you use? liquid or strip?

6. how old is your test kit?

7. how old, what size, and how many fish are in your tank?

 

[CFC]

As skifletch is hinting at i would suspect your KH is very low which means your water has a low buffering capacity. One of the bi-products of the nitrogen cycle is nitric acid which eats away at the calcium buffers in your water, as the calcium is used up the pH drops and the more fish you have the faster this happens.
To rectify this you will have to buy a test kit for KH (carbonate hardness) and GH (general hardness) to see just how low your levels are. If they are not that low then you can solve the problem by adding certain rocks or substrates to your tank, if they are very low then you may have to add buffers to the tank on a regular basis.