pH problem

[kolopedo]

Here is the deal........The tank in question is a 38 gl, occupants are 6 medium sized silver dollars, 1 Kribensis cichlid, and 1 synondontis cat. The tank has been running for almost 3 years now(many occupants in this time).
The problem I am experiencing is that the pH in this tank is very acidic(5 to 5.5) yet my water is very hard(30ppm)...Ammonia and nitrites are perfect. I run a whisper 2 power filter as well as an undergravel filter powered by 2 powerheads so filtration isnt the issue with power to spare. I do weekly water changes of 10 gallons(roughly a third of the water), yet my pH doesn't change, niether does the water hardness. We have rather hard water here in the Twin Cities area, but not as hard as this tank. Any suggestions as to what else I can do(aside from temporary "chemically induced" changes). Could it be the driftwood or the lave rock displays? I am perplexed. My other tank, a 75 gl lake malawi set up is perfect....(7.5 to 8 pH and hardness of 20ppm).

Thank you for any advice!!!!!!!!!

[Cichlid Woman]

If you find out what it is, LET ME KNOW! I'm dying to find a natural way to lower my tank's pH.

Are you by any chance injecting CO2 in there? At first I suspected a bad test kit, but apparently not--its readings aren't that wacked out on your other tank. You're using the same test kits on both tanks, right? Weird--I don't know how to reconcile very hard water with a low pH. I can't imagine what's causing it, and will be very curious to hear.

-- Pat

[wetmanNY]

Hello kolopedo, and welcome to AC, where we have a General Freshwater Forum and a Newbie Forum. In the Newbie Forum we don't pull your tail.

You make one want to ask a few questions:

Where are the many occupants formerly in this tank during the last three years? Do they die in this pH? Is it truly pH 5.0-5.5 or do you mean 6.0-6.5? At the lower pH there will be almost no nitrification of ammonia, but the NH3 will all be in its non-toxic ionized form, NH4. I would expect ammonium (NH4) levels to be quite high, so, when you say ammonia and nitrites are perfect, do you mean nitrites, not nitrates, and is "perfect" the same as undetectable? How old are your test kits for ammonia and nitrate? What brand are you using? If your tank water is harder than your tapwater, and yet you are doing enough water changes to dilute evaporation loss, then your substrate is perhaps a white carbonate gravel?

The acids in your tank that are driving down the pH are all biological waste products. Perhaps your filter media need to be rinsed thoroughly. Do you do this every week?

In fact your other tank, with Lake Malawi cichlids, also has low pH for these fish, which are from an environment where the pH is above 8.0 and hardness above 100ppm. Do you use Rift Lake salts of some kind? Why not?

[RTR]

And which hardness are you refering to - GH or KH? Big difference.

[kolopedo]

I need to make a correction......the water hardness I indicated was prior to convertion to ppm.....the converted total is approximately 530ppm...Also, as far as nitrites and ammonia are concerned, perfect does in fact equal undetectable.
Also to answer a concern regarding previous ocupants of this tank....none where lost to pH problems....in fact, none where ever lost. I have a good trade agreement with my local pet store.
Aside from the weekly waterchange, I also rinse the filter medium well and add new charcoal/zeolite mixture every other week.

[wetmanNY]

Do you think the ammonia-adsorbing zeolites that you say are constantly renewed in the filter are contributing to your level of ___ NH4?

You need to identify the source of the biologically produced acids that are driving your pH to such low levels. Which test kit are you using that gives you results in the range of pH 5.0-5.5?

[RTR]

I'm curious - how did you measure 530 ppm? Still wondering also if you are talking GH or KH.

[kolopedo]

Let me start by offering my sincere apologies to wetman for mistaking his bluntness for hostility...Now let's continue with a little more information...The pH level I listed as 5 to 5.5 is an approximation on my part as the test kit I use only goes as low as 6( I have yet to find a kit that goes lower). However if the test comes out consistantly a yellower shade than the test card even after many weeks of water changes, isn't it safe to assume that the ph is lower than the minimum test value of 6.
Also to expound on the hardness question, the test kit I am using(aquarium pharmacuticals inc.) measures in German degrees(dKH), each drop of solution equaling one dKH or 17.9ppm....the same formula is used for GH.
Please correct me if I'm wrong, but the harder the water, the more difficult it will be to change the pH, correct.
If that is true, which should I try to lower first, the KH or the GH? I can lower the KH by doing a water change with deionized water right? But will that effect the GH? Also where do I get deionized water ?