PH, am I understanding this?

[FrozenFins]

After watching this FANTASTIC stream on PH by Prime Time Aquatics (totally reccomend) I want to make sure I am understanding this properly...

Higher PH = More Basic Water        Lower PH = More Acidic Water

To raise PH you can add woods/ catapa leaves. But only will this work if you have low KH

Generally the lower the PH the lower the KH and vise versa

KH helps to stabilize the PH. The higer the KH the more stable the PH.

 

[CT_]

I think woods have tannic acid so they lower your ph(not raise).  But as you say not by much unless you also have low kh.  You can safely raise ph with crushed coral or other sources of kh.

[Lemon]

how would I lower the kh? 

[FlyingFishKeeper]

You could dilute it in your tank by mixing normal water with a high KH with water with a lower KH such as distilled water or reverse osmosis water. This also applies to GH, and I personally use this to prevent minerals from spiking in my Walstad aquarium since excess minerals aren't removed in a weekly water change. 

[Kirsten]

40 minutes ago, quirkylemon103 said:

how would I lower the kh? 

I wouldn't recommend that, as the KH will buffer all the acidic elements in your tank (like fish waste) from creating wild pH swings, which no fish enjoys.

The way I think of it:

Things that soften the water (remove minerals, lower the GH and KH):
Plants
Driftwood and catalpa leaves

Things that acidify the water (lower the pH if there isn't a high alkalinity buffer/KH source)
Fish waste
Tannins from driftwood and catalpa leaves
Dead/decaying plant mater
CO2 if you inject it for your plants
Vinegar (if you put it in your tank for some reason)

Things that harden the water (add minerals, raises GH and sometimes KH):
Rocks, especially limestone
Crushed coral
Wondershell
Marine salt
Baking soda (sodium bicarbonate)

Things that raise the pH (often goes hand-in-hand with raising KH/GH):
Limestone
Marine salt
Baking soda (sodium bicarbonate)
Crushed coral (slightly, takes a long time to dissolve)

Some fish like a lower pH and softer water, some like a higher pH and harder water. Some might even like hard, acidic water, but I don't know what they are and that must be a difficult parameter to achieve. But even with fish who like soft water and low pH, it's still good to have a little bit of KH to counteract the fish waste and help keep the pH stable.

[Lemon]

21 minutes ago, Kirsten said:

I wouldn't recommend that, as the KH will buffer all the acidic elements in your tank (like fish waste) from creating wild pH swings, which no fish enjoys.

The way I think of it:

Things that soften the water (remove minerals, lower the GH and KH):
Plants
Driftwood and catalpa leaves

Things that acidify the water (lower the pH if there isn't a high alkalinity buffer/KH source)
Fish waste
Tannins from driftwood and catalpa leaves
Dead/decaying plant mater
CO2 if you inject it for your plants
Vinegar (if you put it in your tank for some reason)

Things that harden the water (add minerals, raises GH and sometimes KH):
Rocks, especially limestone
Crushed coral
Wondershell
Marine salt
Baking soda (sodium bicarbonate)

Things that raise the pH (often goes hand-in-hand with raising KH/GH):
Limestone
Marine salt
Baking soda (sodium bicarbonate)
Crushed coral (slightly, takes a long time to dissolve)

Some fish like a lower pH and softer water, some like a higher pH and harder water. Some might even like hard, acidic water, but I don't know what they are and that must be a difficult parameter to achieve. But even with fish who like soft water and low pH, it's still good to have a little bit of KH to counteract the fish waste and help keep the pH stable.

I have very hard water and 7.8 ph but I want chili rasboras and I can't get the ph down I have 2 1/2 6-8 inch cattapa leaves and 14-16 inch(I'm just estimating) piece of Malaysian wood

[Jungle Fan]

quirkylemon103

a RO system might be your answer because buying RO, or distilled water on a constant basis from your LFS, or grocery store on a regular basis would add up to paying for the system fairly quickly.

[Hobbit]

2 hours ago, Kirsten said:

Things that soften the water (remove minerals, lower the GH and KH):
Plants
Driftwood and catalpa leaves

Driftwood and catalpa leaves removing minerals is new to me. Any idea how they do that? Plants removing minerals makes total sense (since they use the mineral same as shrimp/snails would).

[Kirsten]

2 minutes ago, Hobbit said:

Driftwood and catalpa leaves removing minerals is new to me. Any idea how they do that? Plants removing minerals makes total sense (since they use the mineral same as shrimp/snails would).

I don't totally understand it, myself. More just going off guides that claim that those things soften your water, maybe through absorption? More likely they just acidify the water, in my experience.

[Eric R]

I'm not certain that driftwood, leaves, or other botanicals remove minerals from hard water, at least not in substantial quantities. My chemistry isn't the best, but I would guess that the magnesium and calcium ions present in hard water react with the tannic acids released by the botanicals creating calcium tannate and magnesium tannate, which are insoluble and would be removed from the water as a precipitate. However, I don't think you can do this in large enough quantities to reasonably remove hardness from aquarium water. I'd be curious to have this confirmed by someone with more chemistry experience than me however.

The best way to decrease pH, in my opinion, and what I've had success with, is to use an RODI unit or buy distilled water from the store (though the RODI unit will probably be cheaper in the long run, especially if you have a larger tank). You can either mix the RODI/distilled water with your tap water, or use 100% RODI/distilled water and remineralize it slightly. Though how necessary this actually is, I'm unsure. Our aquarium club had a talk from Scott from Tannin Aquatics recently, and he said that he's never actually been able to get his own aquariums below 6.0 ph, even using water with virtually no KH for his tanks. I would definitely recommend either mixing RODI and tap or remineralizing tap water to make sure you have a KH or at least 2 or 3 until you are quite experienced to try using softer water. And whenever you try changing your KH or pH, be sure to go very slowly so that your fish can adapt.

I've been slowly replacing the water in my 55g planted tank with 5 gallons of RODI water at a time, twice a week, over the last two months, and I've lowered the tank dKH from 7 to 3, and the pH from 7.4 to 7 by adding in handfuls of maple and oak leaves.

Edited February 20, 2021 by ererer

[Hobbit]

1 hour ago, ererer said:

I've lowered the tank dKH from 7 to 3, and the pH from 7.4 to 7 by adding in handfuls of maple and oak leaves.

Curious. If I had a dKH of 7 in my 55 gallon I’d be thrilled! I have to work to keep it around 5–I have very soft water out of the tap. Any reason in particular you’re trying to soften yours?

[David Ellsworth]

I wouldn't be too worried about pH for particular fish. Most are pretty flexible. I have some chili Rasboras and have very hard water (8+ out of the tap and high 7's when it sets out 24 hours) TDS is about 630 ppm. Most fish can be pretty flexible with water parameters, but stable parameters are more important. 

 

I do use some RO/DI water and then add minerals (shrimp king gh/kh) because my tap water has 1 ppm ammonia and it plays havoc on quarantine tanks I set up. My display tanks have plants in them and with smaller water changes it isn't as big an issue, just free food for the plants. I can't do large water changes with tap though due to ammonia. 

 

As others mentioned you do want some KH to stabilize the pH, or it could drop dangerously low. Organics that build up in the water help to lower pH, driftwood, leaves, fish waste, carbon dioxide from plants and fish. Unless you're doing something special that reacts negatively to KH like certain shrimp. 

[Eric R]

6 hours ago, Hobbit said:

Curious. If I had a dKH of 7 in my 55 gallon I’d be thrilled! I have to work to keep it around 5–I have very soft water out of the tap. Any reason in particular you’re trying to soften yours?

The particular fish I have in this tank (cardinal tetras, corydoras, and apistogramma) are all native to rivers in South America with low kh and ph. I'm trying to recreate their native habitats more closely, as I feel the fish are more likely to thrive in conditions closest to what they've evolved in.