PH Problems with Fish Tank?

Question

I have a freshwater aquarium and have hight pH. It is in between 8.2 and 8.8. I think this is because (and I talked to a guy at my work told me this is a no-no) I use softwater in my fish tank. I live in Indiana, and we typically have hardwater because of all the limestone. Should I be using hardwater? I have two anglefish and they are doing well. I was also told by a guy at the fish store who tested my water that the pH can be high as long as my alkalinity is high (which does not make sense, if my pH is high, isnt that alkaline?). My nitrates, nitrites, and ammonium are good. I have also only have my tank for about 8 weeks now. I was told that sometimes the cycling can take a few months. Until recently I had about 12 shells in my tank which can raise pH because of the calcium carbonate. I talked to another guy at a fish store and he told me, to use hardwater, something called proper pH (which i already used a ton of, but I think with the soft water and shells it did nothing), and to use a little bit of ROI water filtered by reverse osmosis. The ROI water would not contain much magnesium or anything like that so my pH would be nuetral (from what I understand) and it would over-all lower my pH. If someone could please explain the soft vs. hard water too that would be great. Thanks,

Brad

Answer 1

Brad,

The person telling you to use hardwater instead of softer water appears to be way off course here.  I am assuming your goal is to lower your pH?

Softerwater tends to be lower in pH in light of the aspects you are pointing out.  Your hardness almost always dictates the pH levels.  It's a very rare case where you would have a high pH and low hardness, or reverse of that, high hardness and low pH.  While these two factors, hardness and pH are not the same thing, they interlink with each other.  Especially more so in a fish tank.

Because a fish tank is a closed loop enviroment, the only fresh new water being added, is by you the keeper.  This means there is no natural flow and replenshment of the minerals that would normally be done in a river or lake.  Since this is closed off, water in a mature tank tends to get softer and lower in pH.  

My explanation for why this occurs is that when you clean out a tank, it is impossible to remove every single waste debris that is in the substrate.  There will always be some levels of waste trapped that will continue to decay and eventually produce some carbonic and nitric acids in the tank.  These acids combine with your hardness elements, the calcium and magnesium to "prevent" your pH from lowering.  If you had 0 hardness in your water, and eventually over time, your pH would just directly start going down.  Your hardness elements act as a buffer between the acids and the pH value thus keeping it stable.

Calcium carbonate, shells, crush coral substrates will naturally emit calcium and magnesium into your tank to increase your hardness buffer.  Reverse speaking, things like Driftwood and peat moss tend to soften water.  I can only assume that your goal in this case is lowering your pH?  RO water can help some, but until you address your hardness factor, you will not produce a stable lowered pH.  Eventually it's going to bounce back up due to the hardness in the water, which is why the person telling you to use hard water, is totally off base if you are trying to lower this.

In short, high hardness most of the time = higher pH, lower hardness most of the time = lower pH.  Keep in mind when playing around with pH that this is measured on a logarithmic scale.  This means that say your pH value goes from 8.2 to 7.7, that water is now five times more acidic then it was before.  Shifting values like this too far and too rapid will shock and possibly kill your fish.  This is why I always advocate altering pH via hardness treatments instead of direct chemical treatments.  Chemical treatments cause a rapid sudden large shift, and almost always never stays at the lowered or highered pH simply because they do not address the supporting hardness values.