Kh & Gh what does it all mean?

For some time I have been considering what the different measurements from my tanks mean. For example:
Tank 1- 70 litres, 20% weekly water change, 6 cory sterbai ( + a few fry) 20 galaxy rasbora, 6 microrasbora erythromicron, 2 pseudepiplatys annulatus & 1 amano shrimp (japonica),
Kh = 1 the water goes yellow straight away, never a sign of blue
Gh = 9 has not changed for 6 months

The low Kh means my water has a low ph buffering capacity and the Gh score ?
My tap water measures 6.8 ph and 24hr aerated water before treatments measures 6.8 also, so no major swings there.
Confused and seeking info......
Andrew

Andrew wrote:

For some time I have been considering what the different measurements from my tanks mean. For example:
Tank 1- 70 litres, 20% weekly water change, 6 cory sterbai ( + a few fry) 20 galaxy rasbora, 6 microrasbora erythromicron, 2 pseudepiplatys annulatus & 1 amano shrimp (japonica),
Kh = 1 the water goes yellow straight away, never a sign of blue
Gh = 9 has not changed for 6 months

The low Kh means my water has a low ph buffering capacity and the Gh score ?
My tap water measures 6.8 ph and 24hr aerated water before treatments measures 6.8 also, so no major swings there.
Confused and seeking info......
Andrew

I’m a little questioning of where the confusion lies.

I presume the colour change mentioned is a test kit colour change rather than a tank water colour change. I’m not familiar with all of the test off-the-shelf (as I don’t use them kits myself).

Anyway, I won’t go into a full explanation, but in a nutshell you’ve hit the nail with the link between KH and pH.

The KH is the carbonate hardness, it indicates the degree of carbonate buffering and will relate to pH buffering. The carbonate hardness measure the carbonate anions.

The importance of KH is that it should be such as to act as good pH in preference to trying to obtain the precise pH level.

Carbonate hardness comes into its own when buffering against pH drops during nitrosification or nitrification.

If KH tends to drops too much, then that may be an indicator that there is too much organic muck in the tank.

BUT, I would always give caution to carbonate test as a sign of ‘hardness’ (if strictly speaking) as salts such as sodium carbonate do not cause classical ‘hard water’ under its original definition…..the original definition being related to the ease of causing a soap lather (it is hard to lather soap in hardwater, but sodium carbonate is used as a water softener in industry and in washing machines and bath salts yet it will add to a ‘carbonate test’….the question being, of course, is what is the ‘modern’ definition of ‘hardness’?)

GH is a measure of certain cations (eg calcium and magnesium). Some people may include other cations in their definition of GH. And, of course, the test kit tests whatever it is designed to test.
GH does not have a direct effect on pH even though it may have an indirect effect by virtue of the cation relationship to carbonates (in the KH).

However, GH gives a pivot to something much more important than pH…..redox buffering. Few people bother with Redox measurements, yet I believe them to be of paramount importance. Even if one does not actually measure Redox, it should be realised as more vital than pH.

So, to recap (and maybe slightly too briefly)….KH is important in pH buffering; GH is important in Redox potentials. (there are other issues at stake, but that is they are the main ones for starters)

Ian

Thanks Ian.

I was using the API test kit, in essence when testing Kh you count how many drops before the water in the tube turns from blue to yellow, as I said above mine has NEVER once gone a shade of blue and has always just stayed yellow. So i guess I must have very soft water or at least very little to buffer this water from Ph swings.

So when trying to make my water "hard" for notho's etc, I have to test the nothobranchiius rachovii water for Ph very regularly (daily) and when changing 10% of their water each 3rd day I have to be sure that the salinity and ph and hardness remain constant. I guess I have to be a dab hand at coral sand and salt mixing for the rain and tap water they the rachovii live in.

Hmm now I gotta go find a good quality TDS meter to accompany my simple Ph meter (even though I always rely on my test tube kits as well, the simple Ph probe test is good at checking things quickly.

I remember seeing in a far flung thread a fine photo and piece on rachovii breeding that you posted, I reckon I will try the "tank on stilts" sitting inside the main tank approach. BTW do have you any eggs on diapause?

Regards
Andrew

Andrew wrote:

Thanks Ian.

I was using the API test kit, in essence when testing Kh you count how many drops before the water in the tube turns from blue to yellow, as I said above mine has NEVER once gone a shade of blue and has always just stayed yellow. So i guess I must have very soft water or at least very little to buffer this water from Ph swings.

So when trying to make my water "hard" for notho's etc, I have to test the nothobranchiius rachovii water for Ph very regularly (daily) and when changing 10% of their water each 3rd day I have to be sure that the salinity and ph and hardness remain constant. I guess I have to be a dab hand at coral sand and salt mixing for the rain and tap water they the rachovii live in.

Hmm now I gotta go find a good quality TDS meter to accompany my simple Ph meter (even though I always rely on my test tube kits as well, the simple Ph probe test is good at checking things quickly.

I remember seeing in a far flung thread a fine photo and piece on rachovii breeding that you posted, I reckon I will try the "tank on stilts" sitting inside the main tank approach. BTW do have you any eggs on diapause?

Regards
Andrew

Do I have any eggs on what? that's a bit of personal question.

No, I don't. I had some in storage, but during the house I mislaid them....maybe they will turn up someday.

I'll have to scan the old mud for some of my other species of Notho eggs; not sure if the fish actually spawn though.

I use normally tap water with plenty of peaty stuff and some salt for keeping Nothos; I find that the more stable the water, the better for fish rather than getting exact results. I also tend to keep rachovii at a higher temp than other Notho's (in fact, Discus would be happy in the water).
Changing water....I used a drip system (air-piping syphon into the main tank).

Keep the males and females separate before breeding as either the male will batter the female or he may die prematurely without producing any eggs.

Thanks for the comments on the pictures....they must have been on some of my very first posts on the forum.

I'll get back to you tomorrow on any 'weird' water chem stuff....I have to dash home now.

ian

igmillichip wrote:
=either the male will batter the female or he may die prematurely without producing any eggs.

[/quote]
ian
i think its unlikely that he'll produce any eggs even if he dos'nt die prematurely.

hi all
ian i read somewhere once to incourage clownfish to spawn you can increase the redox .how would this be done
thnks john

Ian,
I am not sure if this has been asked already, but would it be possible for you to give a lecture of sorts on water. I thought I knew a fair bit about water(ph,kh,gh,tds,ec) and then tonight you throw in redox...more reading...

Ian

Redox and freshwater, I would love to hear more about that, there is a thread here (I think it was this forum) on Redox when I was trying to get to the bottom of what the readings mean, what influences the readings and how and why you would want to change them etc., but unfortunately I never got an answer I could understand. Any online research invariably related to marine environments


Daragh

@Derek....well spotted. Excuse my poor grammar there. !!

Redox....and pH...etc...the real importance of these is not always emphasised;
the real explanation why certain pHs are important should only, for example, be seen as a good explanation is that explanation referes to pKa's......no pKa = limited consideration (academically and phyiologically).
Often, however, the practical observations are correct (and from a practical point of view that is all that matters in 99% of cases) but the explanations come a cropper when trying to explain 'unexpected' results.

Redox potential does seem to be something that is missed in freshwater texts....and I really don't know why. Redox potential starts to play a very important role in, say, Discus and Tanganyikan water in particular.
BUT....and here we go with the caveats and the buts, redox is not always good a s simple value: we need to look at what components are involved in the redox potential.

From my own personal perspective, life revolves around redox potentials as a basic principle of life: bioenergetics (discussed on other threads here in brief)takes more than a passing glance at redox potentials.

Anyway, I'm off for coffee now...before I go off on a tangent.

ian

ian, i always worked off very basic principles re general and temporary water hardness and ph. but following your comments on the subject i am getting a much better grasp on some of the side affects that occur when the balance is not right.
maybe the itfs could persaude you to give us a talk on this subject on one of the club nights. i am sure this would attract a large attendence.

john gannon wrote:

hi all
ian i read somewhere once to incourage clownfish to spawn you can increase the redox .how would this be done
thnks john

Hi John,


It would take more than a short post to answer the questions on redox.

Redox is really shorthand for Reduction/Oxidation….but it does go a bit further.
Redox refers to changes in oxidation state (=oxidation number).
Reducing means reducing oxidation state; oxidising means increasing oxidation state of a system.
If we consider systems where the change of oxidation state is via transfer of electrons, then Reduction is the gain or electrons and Oxidation is the donation of electrons.

It would usually be the electron transfer processes that in question in general redox reactions where we want to consider for redox potentials. The overall Redox (or simply Reducing) potential is a measure of the free energy of a system…and it is usually expressed in Volts (but could be expressed in other appropriate units).
When we have a battery redox reaction, we can see the electrical output from that reaction; in other systems it would not be so easily measured.

Now, I have to be careful here as one of my favourite topics in biochemistry was a process called oxidative phosphorylation ……and the toxicology of it (in particular partial poisoning of the process in respiration)….so I’d have to stop myself going off into a mad philosophical lecture on it 

Adding normal cooking salt changes the redox, adding cyanide changes the redox, adding new water changes the redox, and changing pH changes the redox.
However, the system works as a whole and so a change in redox in one direction may be opposed in the other (ie something added to system to reduce that system, and something added elsewhere may oxidise that system).

So, as you can see there are lots of ways to alter redox, but it needs to be appropriate for the animal.

As for spawning clown loach, I’ve never spawned 2 foot monsters before.
So, I’ve never had the opportunity of knowing what happens or what precedes breeding.

With many fish, we see breeding after a water change (eg corydoras).

For general fish health anyway, I’d be a fan of the water changes for many reasons….one of them being to replenish GH or to maintain a reducing environment.

Often we may find that even if the GH test shows a constant GH, the GH may actually be lowering with time. The test kit may not be measuring the right type of calcium/magnesium……it has to be in the correct oxidation state (redox state) to be ‘correct’ for a biological system, the test kit may not be measuring that correct oxidation state.

A change of water or addition of a GH stabiliser may replenish the Reducing redox potential (and bear in mind that aerobic and anaerobic systems may have differing preferences wrt being in a reducing redox or an oxidising redox….that is of great importance to a healthy tank)

Built up of acids in the water may lower the reducing potential of the water (the definition of an acid is that it is a special kind of oxidising agent); water changes will generally reduce these oxidising effects……but in some fish massive water changes in below standard water can cause a major disturbance of redox that the fish become stressed (and for good reason…..I see the difference between living and non-living is actually the way that a living organism controls its redox potential).

pH, KH, and GH are things often used to describe water chemistry….but maybe that is because they are fairly easy to measure and have a long history of understanding in fish keeping. That doesn’t mean that they are the be-all and end-all of everything….often it is a coincidence that a given pH or KH or GH etc etc happens to relate to the correct water conditions.

So, I can’t say how to get your clowns to spawn….but there may be food for thought.
It may well be worth looking at the natural history of the clown loach in the wilds to look at when the breeding season is, and do they migrate or not. That is the real start, and then go from there.


Ian

yeah i was lost at "last post by igmillichip" even the "Hi" part, i was thinking maybe thats a scientific description for something else.

hi ian
im sorry for been ambigious with my last question the fish in question are amphiprion percula [marine clownfish]and after searching were id read about increasing the redox potential it said to do this by adding potassium permanganate [whatever the hell that is]but it never said what it was and how much to add so i was very dubios to say the least.
thanks john
ps as derek said if we could get you to do a talk at one of our meetings it would be great

I thought I understood this subject - now I realise I barely scratched the surface.

I test my kh & gh - somehow the KH is higher than the gh. I know this probably depends on what is actually being measured as part of gh/kh.

I think I'll just keep my fish in Evian;)

john gannon wrote:

hi ian
im sorry for been ambigious with my last question the fish in question are amphiprion percula [marine clownfish]and after searching were id read about increasing the redox potential it said to do this by adding potassium permanganate [whatever the hell that is]but it never said what it was and how much to add so i was very dubios to say the least.
thanks john
ps as derek said if we could get you to do a talk at one of our meetings it would be great

I must have totally misread your post John....for some reason I read it as Clown Loach. I think that I must also get me a dunces cap and stand in the corner.

I'll get back to you on the topic as I'm quite pushed for time at the mo.

ian

igmillichip wrote:

john gannon wrote:

hi ian
im sorry for been ambigious with my last question the fish in question are amphiprion percula [marine clownfish]and after searching were id read about increasing the redox potential it said to do this by adding potassium permanganate [whatever the hell that is]but it never said what it was and how much to add so i was very dubios to say the least.
thanks john
ps as derek said if we could get you to do a talk at one of our meetings it would be great

I must have totally misread your post John....for some reason I read it as Clown Loach. I think that I must also get me a dunces cap and stand in the corner.

I'll get back to you on the topic as I'm quite pushed for time at the mo.

ian

I’m a little cautious about info stating that RedOx should be altered for Marine fish to get them to breed.

Marine water should be pretty stable for a given water-level from hour-to-hour, day-to-day, week-to-week etc.

This is contrast to many freshwater systems where there are seasonal changes that may (and I say ‘may’) affect breeding patterns.

If the marine water is in a state that requires specifically changing redox potentials for breeding, then maybe that is really a convolution of the water not being right in the first place to keep the fish in the first place.

Now, if the (marine) fish migrates to differing regions to breed, then that is a different matter and the fish may be experiencing a change in redox anyway.

I would also be a little cautious of methods to change RedOx…..or to ‘increase it’….why?
Really we should be talking about either a ‘Reduction Potential’ or an ‘Oxidation Potential’.
Is the advice for increasing the potential talking about increasing the Oxidation Potential or the Reduction Potential? (and this is where RedOx can be a bit tricky….ie what is actually being increased?).

RedOx is a thermodynamic property.
It relates to a drive in one direction or other of a transfer of electrons (if the system involves electron transfer).

If the drive in one direction is very very much favoured (thermodynamically) then the drive in the opposite direction will be very much unfavoured.

Eg the reaction of sodium metal going to sodium ions (oxidation) is very much favoured (and is shown by the redox potential for that direction of change), but the opposite reaction of sodium ions going to sodium metal (reduction) is unfavoured.
But, the reaction of gold metal to gold ions is not favoured well.

Ultimately, Redox potentials can be useful, but they lack detail (a bit like pH) as to what exactly is causing the potentials.

I think that using potassium permanganate to alter redox potentials needs to have the question of ‘do we really need such a drastic oxidising agent to be added?’….in some cases, permanganate is a great agent, but in other cases the answer is that good water management should sort that out.

Maybe where redox potentials have been changed for breeding marine fish, it may be that the original redox was sub-standard for normal living.
It’s a bit like giving someone who hasn’t eaten for a while some good fruit….and then finding that they can now do some mathematics, and then we come to the conclusion that the Vitamin C in the fruit increases brain-power!!! (and ignoring the fact the person was originally starving to death)

thanks ian
i think well just stick to the water management and patience method
thanks again
john

john gannon wrote:

thanks ian
i think well just stick to the water management and patience method
thanks again
john

I'd favour and go for that as well.

Best of luck.