Persistant low pH

ericemckee

Hi there.
I've had my 50 gal established for over a year now, but have noticed that the pH stays very low, around 6.0 or lower, and if I bring it up with chemical products, it will always gradually return to that level. I have also noticed that when the pH goes low, some of the fish develop lesions or cottony growth that goes away with broad-spectrum disease treatment.

I have only a couple of resin tank decorations, and try to be careful about the amount of food I give. Very low nitrate, very low nitrite, moderatly high hardness of the water. Standard gravel substrate from a pet store. Monthly 20% water change with change of filter medium is my usual habit. I can't keep plants in the substrate because the fish dig them up, so there is usually about 15-25% of the top surface area covered by floating plants.

The aquarium is pretty tightly covered, though I don't know if that has any affect on the water chemistry.

Any suggestions on what might be the culprit here, or good long-term solutions? I am leaning towards adding seashells, but since the water is already very hard, I don't know if that would be a good idea.

Thanks,
Eric

92smokeaccord

add crushed coral.it maintains a higher level ph for ciclids but in ur cause if its tooo low then it will raise it quite a bit and keep it there.what is stocked in you tank and what are the other parmaeters?

ericemckee

Tinfoil barbs, gold barbs, silver dollars, one of the larger tetra species, and a lonely rainbow praecox (sp?). Probably a dozen fish total. I'll post test-strip results later.

Geomancer

Hello and welcome.

pH dropping over time usually means you have a low KH. Hard water does not mean high pH, or vice versa.

Do you know your GH and KH, the actual numbers. When people (especially stores) say "Hard" that can mean a lot of things. I use to think I had hard water because the shower head has calcium deposits on it ... but in reality my tap water is extreamly soft.

The fish you have listed are soft, acidic water fish though. So I don't think it should really bother them too much (but maybe it's too low for the tinfoil barbs). The pH swings caused by the chemicals, however, does create stress on the fish which does invite disease. A pH in the high 5's to low 6's isn't unusual for a lot of soft water fish.

Byron

Yes, we need the numbers for GH and KH, and of your tap water; these you can ascertain from the water supply folks, they may have a website or can tell you directly. We will assume the GH and KH in the aquarium is roughly the same, which it will be unless you specifically target it with something to raise/lower.

Also, what is the pH out of the tap? And when testing tap water pH, put some water in a jar with a tight-fitting lid and shake it vigorously for several moments to dissipate out the CO2, or you can get a false pH reading.

The fish are soft water fish and acidic water. The symptoms you mention could result from too acidic a pH. Are you certain the pH is only down to 6, and not lower? Most test kits have 6 as the lowest result so if the colour is yellow it could be much lower. I have tanks down around 5, but the fish I have in them are fine with this. This is not the case with those you mention, so bear this in mind.

Once we know the GH and KH of the tap water we will have a better grasp of how to remedy this. As you've already seen, using chemicals to raise pH does not work, and as someone said this is almost certainly due to the KH. We need to address the KH and perhaps the GH in order to adjust the pH. If you want some background info, have a read of this article:
Water Hardness and pH in the Freshwater Aquarium

However, having said all that, there is a real problem: you are not doing frequent enough water changes, nor are you changing sufficient water. Water changes must be weekly, no matter what. The volume can depend upon the specifics of the tank, live plants, type and number of ifsh, feeding, etc., but I always change half the tank every week. This is a significant way to maintain more stable parameters. Fluctuating pH is very stressful on fish; the outward signs are serious in themselves but not as serious as the damage that is veing caused to the fish that you can't see: stress. Here's info on this:
Stress and Freshwater Aquarium Fish

Allowing the tank to go a month with no water change is bound to cause bioloogical trouble, and the lowering pH is certainly related.

Byron.

ericemckee

My local water company reports "total hardness" as approx 100 mg/L (moderately hard) and the "calcium hardness" as 60 mg/L. If I read correctly on the links above, that's about a 10 GH and 6 Kh, though I could be mistaken. pH of the local tap water is approx 7.5.

Byron - you are correct in guessing that my liquid pH test kit only reads 6.0 as the low, and the water is likely even more acidic than that. I've been adding a cap of "pH up" and buffering solution daily to try to bring it up gradually, but haven't seen a read above 6.0 in the first three days of doing this.

Test strips today showed no chlorine, nitrate or nitrite. Alkalinity (kH) per test strips was somewhere between 40-80 ppm.

Geomancer

The conversion is actually 1 dGH = 17.848 ppm (mg/L)

So that means your water is 5.6 dGH which actually falls into the 'soft' category (anything under 8 dGH) for fish.

I'm not entirely sure how to raise KH & pH only slightly, enough to keep it under 7, but higher than 6 and still be soft water. Usually you can add small amounts of dolomite, aragonite, or crushed coral to the filter, but that might make it jump too high.

I'm sure Byron will have an answer, he's omnipotent in the fish world ;)

ericemckee

That's odd, because the water company reports their water as "moderately hard to hard". Test strips also show my tank water as between moderate and hard water.

AbbeysDad

What is the pH of your tap water?

Frankly I think Byron hit the nail on the head - you need to do weekly water changes of sufficient volume. (20% monthly is insufficient.)
This will likely solve your issue and no longer require additives to adjust for pH.

I'd suggest you do at least two 50% water changes spread out this week, then do anywhere from 20% up to as much as 50% weekly.

Byron

Geomancer answered this, and I agree. 100 mg/l is basically the same as 100ppm, which divided by 17.9 equates to 5.5 dGH. [I like using dGH and have used these in our profiles because the numbers are smaller are more easily understood, but ppm is also common.] The KH which is what buffers pH is very low at 60ppm, roughly 3 dKH. But this is still sufficient to buffer what you are attempting to adjust with the pH up. Please don't use this stuff, it is harmful on fish; and do a couple of major water changes as AD suggested first to get this chemical out of the water, but also to begin stabilizing the biological system.

We must assume the water folks' numbers are accurate, notwithstanding any terms they apply to them. You could take a sample to a reliable fish store to test GH and KH for comparison. Up to you, but I tend to think the numbers must be reliable. This is why the pH will easily lower, due to the natural acidification of the water as organics are broken down by bacteria and the resulting CO2 produces carbonic acid. This is perfectly natural and not a problem, except that the p|H is lowering too far. But the weekly water changes will help stabilize this.

The next step would be to buffer the pH slightly. This is easy to do, I do it in two tanks. Get a small bag of dolomite or aragonite gravel; dolomite is better in my experience, but seems harder to find these days whereas aragonite gravel is available in several stores. It only takes a small amount, I use 1 tablespoon in the filter of my 115g tank and it keeps the pH around 6.4 instead of 5. In my 90g the same amount is keeping the pH around 6.6-6.8, so it takes very little. And this lasts months. But first, get on track with the water changes and after a couple weeks of testing the tank pH regularly see what is happening. The next step may not be needed.

When testing pH, always do the test at approximately the same time each day. This is because the pH will naturally fluctuate during the day and then during the night, so testing each day at say 7 am, or 12 noon, or whatever, will give you a more accurate idea of what is happening. And always do it in daylight if at all possible, because artificial light can affect the colour. Daylight, but not direct sun, is best.

Byron.