Something's driving up my hardness

[ApistoNerd23]

I've googled the heck out of this and called a couple of local fish stores and I cannot figure out what's driving my PH, KH and GH up.

I figured I'd throw it out here to see if anyone has any ideas that might help.

Over a year ago I switched to 100% RO/DI water since I had hardness of like 8-12 dGH and knew I wanted to keep dwarf cichlids.

Since then the hardness has come down but it's still like 3 dKH and 5 dGH.

I bring the DI/RO water home and test it. 0, 0 and PH 7.0.

I add it to my 55G and test in a few days. 3 dKH and 5 dGH, PH 7.8.
I add the same water to my 12G and test in a few days also. 1 dKH and 1 dGH, PH 7.0.

Both tanks have plants, Manzanita driftwood (same tree) and rocks (took rocks from the 55 for the 12). The amount of decor is about the same proportionately from tank to tank.

The only thing I can think of that's different is the substrate. One is home depot sand (12) and the other is ADA Amazonia with a fine gravel.

I took some substrate from both tanks and put it in some clean water and I tested it after letting is set over night. No difference. 0/0/7.0. Should I let it sit longer.

Any thoughts on what else to test or look for?

Thanks for any input, this is really weird. All the google searches I see mostly come up with "Tap Water" or "Soil meant to raise PH." I use neither of those.

 

[regani]

if some of the rocks in your 55 are sandstone or something similar, they can raise GH, KH, pH.
you said in your 55 there is "ADA Amazonia with a fine gravel", any idea what the gravel is? could also be crushed sandstone or similar.
you can test the stones and gravel by taking them out and pouring some vinegar over them, if you see some bubbles form, that means those rocks contain calcium carbonate which wil raise your water values

 

[Mike Wise]

I agree with regani. It's either the substrate of the rocks. Vinegar is a fairly weak solution of acetic acid and may not always detect carbonate rocks. Go to a hardware store and buy a small quantity of muriatic acid. This is a less pure, industrial grade of hydrochloric acid. Add 1 part muriatic acid to 9 parts water (NEVER ADD WATER TO ACID!). This will give you a better idea where your carbonate hardness is coming from. I will say that 3° dKH isn't terrible for most apistos.

 

[tjudy]

The vinegar test will only indicate carbonate hardness, but there are many more ions that will test positive on a general hardness test. Feeding, fish waste and plant detritus will drive up general hardness (though admittedly not as much as you are experiencing). Based upon what you described, it can only be the substrate in the 55 if the rocks in the 12 are the same as the rocks in the 55. How often do you do water changes, and how large?

 

[ApistoNerd23]

Thanks for the replies!

Regani:

I'm not sure what the gravel is. It said "Rockman." The place I bought the gravel from knew I was interested in softwater fish and they are by far the best in the area (ie, always have apistos, discus, panduros etc). I would guess that they would not sell me gravel which would raise the hardness. But that's a big assumption on my part.

The stones are the same ones as are in the 12 gallon tanks which is <=1dKH and <=1dGH. I would think that rules them out but maybe not?

Would the same test apply for the substrate? ie, put the substrate in the acid or vinnegar?

Mike Wise:

Even if the KH is ok, is the 5dGH a problem for most apistos or am I good there too? I would really like to get to where I'm near 0 on both and then moderately tinker if needed, but maybe I'm chasing something I don't need to tinker with.

What do you guys think of my substrate in a glass test? After getting 0/0 overnight, I stirred the glasses last night and will test again. I'm not even sure if this test is valid though.

One other thing I just thought of, I run an airstone all night in the 55Gallon, which I don't in the 12G. Could that be a factor? I would think that would drive the PH up but not the hardness. Or am I wrong about that?

Ted:

On the 55 and the 12 I usually do a 30% water change every two weeks, on average. Is that not enough? I doubt it's on the too much side. And when I do the water changes it's 100% DI/RO.

Thanks again for the ideas!

 

[regani]

I would test the substrate just to be sure. As Mike suggested, the test works better with stronger acids, I am just a bit hesitant to recommend those as you have to be careful in handling them - more difficult to hurt yourself with vinegar

with just the substrate in a glass of water it may take some time before you see a change.

The airstone shouldn't affect your readings for KH and GH

 

[Mike Wise]

Total hardness (dGH) has less effect than carbonate hardness (dKH) when breeding softwater fish. Until you reach around 10° dGH, I doubt that you will see much difference. Funny, as a minerals exploration geologist I carried a bottle of HCl with me whenever I was in the field and never thought it really dangerous. I must admit I had a lot of holes in my shirt and jeans pockets!

 

[ApistoNerd23]

I'll try the vinegar and see what happens and if I get nothing I might be braver with the acid.

After all the replies and such I'm thinking it really must be the substrate (either the rocks or soil)... I put the sand from the 12g, the gravel and soil from the 55G and a bunch of snail shells from the 55G (who knows?) into glasses of water... after two days still nothing on the water test.

I really can't think of anything else it could be...

Thanks for the information about the dGH etc Mike. I want to change the 55 out to a sand substrate some day down the road... maybe I just won't worry about it TOO much until then.

 

[ApistoNerd23]

Update: I just tested all 3 water glasses and it looks for sure like the substrate/soil from the 55 has moved from 0ppm dGH to 25dGH while the other two have stayed at 0. The dKh hasn't moved noticably but the non 55 gallon test strips stayed at 0dKH while the 55 gallon sample got like 40/80 coloring around the edges.

I admit it's not perfect science but it's still interesting test results.

 

[Simon Morgan]

You don't really need zero hardness, even for breeding apistos. I use a TDS meter and my water is 50-100ppm depending on the project.

 

[ApistoNerd23]

Update: It's definitely gotta be the substrate. I checked the water sample again and it's way higher than the sand sample.

Do you guys strongly prefer a TDS meter over solution based testing? It seems like you can't split dKH vs dGH with the TDS meters I was looking at but maybe the total is more important than the type of hardness... I like the idea of getting an accurate reading quickly vs strips or drops.

 

[dw1305]

Hi all,
Yes, you can largely ignore dKH and dGH and just measure the total amount of dissolved salts, the advantage of this is that we know that most Apistogramma spp. come from water that is poor in all dissolved metals, not just carbonates and multivalent ions. As water (really dilute solution) gets nearer to pure H2O, and the carbonate buffering declines, pH becomes a meaningless measure, this is not true of EC, which remains largely linear over the scale that we are interested in.

The advantage of a conductivity meter is that it is simple to operate and doesn't need frequent re-calibration. I've no idea of any of the parameters of my tanks, other than conductivity, which I retain at about 100 microS (I don't keep any Black water species), even though some of the tanks are next to a proper analytical lab.

cheers Darrel

 

[Mike Wise]

As Darrel wrote, separating total and carbonate hardness isn't really important if the water is really soft. If your water is moderately hard, it is a good idea to determine carbonate hardness if you are keeping blackwater fish. My water is naturally very soft so I rarely use a chemical KH indicator.

 

[dw1305]

Hi all,
Mike wrote

If your water is moderately hard, it is a good idea to determine carbonate hardness if you are keeping blackwater fish

Mike is right and I should have written a bit more explanation, it's probably easiest if I put in some figures.
The ordinary lab. de-ionised water has a conductivity in the range of 0 - 3 microS, distilled water (from an old fashioned steam distillation unit) is about 20 microS, our rain-water varies between about 180 microS to 80 microS (lower in the winter, and this is an area with calcareous geology), and our tap water (from a deep limestone aquifer) is in the range of 650 - 800 microS.

For the rain and tap water an ordinary hardness kit is fine and will find that the dGH and dKH are similar in both cases, as almost all the dissolved salts are derived from calcium carbonate.

cheers Darrel

 

[ApistoNerd23]

Thanks Mike and Darrel. That helps a lot to know that splitting the dGH and dKH isn't as critical as I once thought. Maybe it's coming from the plant tank world and CO2 injection where dKH is desirable for stable CO2 levels.

I did buy a TDS/EC meter and found that my 55G, which was the one I originally posted about, 180 microS and 92ppm. From what I've read from search this forum, that doesn't actually seem all that high after all.

Based on the fact the test glass of water has gone from near 0 RODI (also tested) to 86 microS / 43ppm and the sand only substrate has only moved half that much, I'm still sure the substrate in the 55 is the source of the higher readings. I tested my tap and it was 536ec/270tds LOL. I'm glad I stopped using it! It was great for the plants though! My RODI only water at present has really put a hurtin on most of my plant except the swords and crinums etc.

Am I right that 180/92 is fairly soft?

 

[Mike Wise]

I don't know if there are established dividing lines between what is soft, moderately soft, moderately hard and hard. I would consider your water to be on the soft/moderately soft borderline.

 

[jaafaman]

If you were to jump to Wikipedia's listing, it starts out with "soft" water, causing the list to be questionable

Soft: 0–60 mg/L
Moderately hard: 61–120 mg/L
Hard: 121–180 mg/L
Very hard: ≥181 mg/L

so I jumped to one of the government's water quality sites. The USGS uses the same values, but starts its scale with "very soft" at the base, with 181-250 mg/l as "hard" and anything >250 mg/l as "very hard"...