low PH with high GH - help

[Nina]

So, I'm new to fishkeeping -- I started in February and cycled for a few weeks before adding 6 neon tetras (which are all doing great) to my 10 gallon tank. It has a few plants (anubias, a few stems, and some dwarf sagg that is starting to carpet) and gravel substrate (no driftwood). I attached the anubias to a small rock I found (and boiled). I think it is quartz or an agate and it didn't seem to change the water parameters for the first two months.

However, in the last few weeks I've developed some weird problems:

1) I have low PH (6.3-6.6) even though my tap water is 7.0. I can't raise it above 6.6, which is frustrating because I'd like to add guppies or other fish that might need a neutral PH.

2) My tank has developed very high GH (the very purple square on the aquarium co-op test strips) even though my tap water is VERY soft (nothing registers on the test strips). I've confirmed these parameters with 3 brands of test strips, and have confirmed the PH readings with the strips and liquid test kit. Also, GH is very high while KH is low (it barely shows up on the test strips)

The only things I add to the water are Seachem Prime, a variety of fish foods, Easy Green (per instructions), and a few Aquarium Co-op root tabs (when I started). I added 0.7 pounds of crushed coral to the substrate when I began and ran a small bag of it in my filter for a week several weeks ago -- still, the PH stayed at 6.6.

I'll admit there are reasons for acids in there -- I let the tank get dirty for the first 1-2 months thinking it would fertilize the plants (not realizing that 4-5 small plants don't need all that fertilizer). That said, I've changed my ways and after some major (60-80%) water changes and cleaning I'm gravel-vacing now. I've always done a ton of water changes on this tank to keep the nitrates down to 20-40 (sometimes 3 or more 30% water changes a week). 

I'm so confused because it seems like low PH is usually associated with low hardness. My PH is low but GH has been very high for a few weeks now and KH is relatively low (barely registers on the test strips). What could be going on? How can lower the GH and raise the PH?  

Thanks!

[tonyjuliano]

Too much fertilizer...

As the ammonium-N in fertilizers undergoes nitrification (conversion of ammonium to nitrate by bacteria), hydrogen (H+) is released, which can increase acidity. As the percentage of ammonium increases in a given fertilizer the acidifying potential will also be increased, thus reducing pH.

[Mmiller2001]

You might be confusing things. GH is water hardness (amount of Ca:Mg). KH- Carbonate Hardness(often confused as hard/soft water) is the measure of carbonates and bicarbonates in the water. GH has almost no impact on pH, but KH impacts pH. So low KH water will have a low pH and vice versa. Active substrates or rocks can alter things to a degree and you will want to account for their affect on your water.

[Nina]

It is definitely confusing me. I just checked my tank with the Aquarium co-op strips to be sure. The strips list "Hardness(GH)PPM)" and "Buffer(KH)PPM). My Hardness(GH) is around 300 and my Buffer(KH) is near 0. My PH is fairly stable at around 6.6.

[Mmiller2001]

23 minutes ago, Nina said:

It is definitely confusing me. I just checked my tank with the Aquarium co-op strips to be sure. The strips list "Hardness(GH)PPM)" and "Buffer(KH)PPM). My Hardness(GH) is around 300 and my Buffer(KH) is near 0. My PH is fairly stable at around 6.6.

So the near 0KH is the reason for low pH.

[Isaac M]

Hello @Nina, pictures of your aquarium can really help if you are willing to post them. It helps people see any potential sources of gh in your aquarium like the substrate, rocks , etc as @Mmiller2001 commented. 

kH or buffer is what is directly correlated with pH. If you want to increase your pH, I would recommend crushed coral. It is likely that your pH dropped due to the removal of crushed coral and acidification process @tonyjuliano described.  

If you want your pH to go up, you have to increase your kH. That can be done by keeping the crushed coral in the aquarium. It must stay in there however the whole time, it cannot be removed after one week or else the change will just be temporary. 

As for the gH, we need to remove whatever is in your aquarium that has increased it. Guppies however do like high gH as well. 

[Nina]

Well, the PH has been pretty stable - 6.4 raised to maybe 6.6 after running lots of coral the last few weeks (most coral is still in the substrate, I removed the little bag in the filter after the PH started going down again).  I will try to get a picture but I already freaked out and resorted to raising the PH by .2 or so ever 2 hours with baking soda, gravel-vaccing the substrate, and capping with black sand, because a friend brought over 3 guppies he thought I'd be ready for (so tank looks entirely different than it did a few hours ago). So far, the guppies have been in there 3 hours and are still alive and I'm getting close to 7.0 PH. Tested some more and only the aquarium co-op strips have me testing at a GH of around 300. Every other test now says I have low/moderate GH. Buffer is increasing but still low. I am being VERY careful with the baking soda because I know it's not a good long-term solution. 

[TheAdmiral]

15+ years of aquarium keeping has taught me that stable pH is far more important than a specific pH. 6.4 is not all that low (unless you are keeping certain cichlids that really need 8+). But trying to maintain a pH that is outside what your local water allows is a nightmare (for you and the fish). I use a lot of crushed coral myself (in substrate generally but also occasionally in the filters) as a buffering agent against pH swings which as a side effect keeps my pH around 7.8. My city water here in metro Atlanta comes out of the tap around 8+. Having the crushed coral really helps keep the pH stable and protects against swings caused by overfeeding or decaying plant matter. 

So really it depends on your tank set-up, If you are running a Walstad, then you don't want to vacuum or add fertilizer. If you have a traditional gravel/sand bottom tank with mechanical filter, then you will likely want to supplement with fertilizers and gravel vac the surface (so as not to suck out your root tabs). More plants = more ferts. Easy Green says one squirt per 10g but if it's not heavily planted and or not high light, you may only need 1 or 2 squirts a week. It's trial and error really until you get the feel for it.

Long story short though, I personally would not worry about any pH between 6 and 8. And if you find your equilibrium is in the mid to low 6's, get yourself some discus and revel in my jealousy. 

 

Edited May 20, 2021 by TheAdmiral

[Kellyo]

I have low kH, low pH and high gH naturally from the tap 30+drops of API gh. (5 gallon) I've amended with crushed coral to the substrate to raise kH and stabilize pH to in and around 7.8. My question is, I'm setting up a new 20 gallon long. I want it heavily planted. I'm planning on Fluval Stratum and root tabs. Can I/should i cap the Fluval with crushed coral? Will this affect plant growth? Can I/ should I/ how do I/ lower gH?

Ok more than 1 question. I'm itching to order my plants. The 5 gallon took 8 1/2 weeks of fishless cycle, due to multiple stalls, (I think due to low pH 6 ( or less) and 0 kH.) Sorry such a long post, but I want lots of plants and not sure if this combo is a good idea.

Also, 5 gallon has 3 Amazon swords and 1 Betta.

Thanks!

[tonyjuliano]

On 6/26/2021 at 4:17 AM, Kellyo said:

I think due to low pH 6 ( or less) and 0 kH.)

It’s the “zero” kh that stalled your cycle.  The nitrification process cannot function efficiently (or at all, really) without some level of alkalinity. 
 

GH is of much lesser concern in a freshwater environment.

Edited June 26, 2021 by tonyjuliano

[ARMYVET]

Only way to lower GH is to water change with water that is low in GH like r/ o water.  
 

To raise KH/ alkalinity you need to add calcium carbonate in one form or another wether it be from a buffer or using crushed coral.  Just know that the Stratum naturally lowers Ph so adding the crushed coral as a cap would be beneficial in your case.

 

 

Edited June 26, 2021 by ARMYVET

[Kellyo]

@ARMYVETthank you very much! I've spent countless hours on the internet researching. You answered my questions only an hour or two after I posted! Many thanks!