After the first death, all the inhabitant seems to be infected by some kind of disease. All of them now have red gill! Im afraid this will lead to a wipe out!

Any advice would be very useful!!!!

I'll check the water now and see if it's ammonia poisioning

reading shows
Ammonia 0 ppm
Nitrite 0 ppm
Nitrate 10 or 20 ppm (Can't tell cause' they're almost the same color).

This can't be ammonia poisoining...

Hi Nathan,

If all fish have red gills and there is no ammonia or nitrite (and hasn't been) then this is likely to be about incorrect water parameters.

From your previous posts:

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7.5 is not very high for fish that need high alkalinity.

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This is too low

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As I'm sure I've said before, gH has no effect on pH. kH is what raises and buffers pH. Mbuna need a high pH. Ideally 8 or over.

Using the right buffers will prevent pH from rising beyond a safe level as once a certain saturation is reaches, pH will not rise further. Mbuna pH ranges up to 8.5

Your tap water has gH and kH both at 3. The tank gH is only 5 and you haven't said what the kH is. You must raise these as Mbuna need hard alkaline water. If there are insufficient minerals and salts in the water, the fish struggle to maintain a proper balance of fluids in their bodies and they suffer irritation such as you are seeing with the redness in their gills.

You must raise gH and kH in the tank (gradually over several days) to at least gH 10 and kH over 10 - around 12 should be good. Once they are raised you need to match that in every water change.

Thanks for reply FL
I understand, it's just weird that all my fish have been fine for a few months but now this happens.

I really have no idea how to raise gH, I can raise kH is raising gH won't be easy. I've been looking and can't find the right reagent.
Yes I forgot to mention kH, I just tested it this morning and forgot about how many degree but it was over 8. And sorry about my carelessness, I tested gH again but do it properly this time, the result shows 7 degree, I don't know how it raise to that though, probably due to the rocks? Last time I was distracted and assumed my gH was only 5.

Is there any way to increase gH but not using espom salt?
Also pH in my tank is currently 8, I could bring it to 8.2 but I'm afraid that I'll over dose and have it raise too much.

I will get more crushed coral if needed

More coral in the tank won't help. Coral does raise kH and gH, but it does it very, very slowly and its use is more to prevent these from falling than it is to actually raise them to any great degree. That is why when your tap water is so far off from the right parameters it has to be correctly adjusted before going into the tank.

The reason your fish have taken a while to show signs of distress is that incorrect parameters do take time to cause visible problems. Initially, though the fish's system is struggling to cope, there may be no external evidence of a problem.

The situation is that these fish have been living in water that is too low in hardness and alkalinity. Every time you do a water change, any improvement made by the use of crushed coral is negated by the new water going in - and your fish are not only living in the wrong parameters, but on every water change there is a downward swing which makes things worse.

As I've said many, many times now, using a buffer to raise the kH, assuming it's the correct kind of buffer, won't push the pH beyond a certain point. There is a limit to how high pH will rise with a particular buffer, such that beyond a certain dosage adding more will ony affect kH and pH will stop rising. What are you using to raise kH?

You must raise the gH as well as kH: a lack of hardness will make the fish ill. The easiest to use are Epsom Salts (MgSO4-Magnesium Sulfate) for gH and bicarbonate of soda (NaHCO3).

An alternative you can use for gH is Calcium Carbonate (CaCO3).

The only other way to achieve this is to have a large container full of water with a filter full of crushed coral and/or oyster shell to raise the gH/kH over a period of time and then use it for water changes. However it will take too long for the gH and kH to rise high enough from the starting point you have and so isn't going to be practical.

So what exactly should I do?
I use pH buffer in every water change to achieve make the new water match the water in the tank.
The one I use is made in taiwan, can't find Us or Uk products here.

CaCO3 is in limestone right? Limestone for building would not be so hard to get but for aquarium, I've seen none. Is it safe using building limestone for fish tank?

bicarbonate of soda, It's baking soda but someone mentioned it usually has additive if I buy it in general stores and not safe for fish. If you confirm baking soda is safe then I could use that to raise my gH.

About the product I use, I have no idea how high it'd reach, I'll do some test tomorrow and see what happens.

As far as I know Nathan Epsom Salts are avialable in most countries as it's used in many medicinal over the counter treatments for us mere mortals. Have you asked in a chemist/drug store?

Not sure what the translation would be though I'm afraid!

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Limestone itself would be no help in the water for changes as it would take too long to have any effect. You need the actual powder, which may be available from a chemist, Epsom Salts (Magnesium Sulfate) which will do the same job will almost certainly be available at a Chemist's as V said.

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In the UK we call it bicarbonate of soda. In the US they call it baking soda, but there is also baking powder in the UK which is usually a mix of bicarbonate of soda and cream of tartar. You want plain bicarbonate of soda with nothing else added. The label on the pack should tell you, or again, ask at a Chemist's as it should be available there.

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NO, you can't use it for gH - it ONLY raises kH. To raise gH you need magnesium sulfate or calcium carbonate.

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What product do you use? What are its constituents?

All these compounds will be readily avaiable just about anywhere in the world - really, they will, it's just a matter of looking in the right shops. A general store or a pharmacy/chemist shop are the most likely.

Yes Nathan as someone working in a chemist I have to agree with Fishlady and Violet.
As I'm unsure if they have 'Epsom Salts' in Vietnam if I were you I would just write down MgSO4 as that is internationally recognised (Epsom is a place in england so it probably has a different name over there) and ask them if they have any products that contain this and that would be safe to use in an aquarium.

If you can get it in a hydrated form (MgSO4.7H2O) even better as it will make using it much more simple (anhydrous MgSO4 absorbs water from the air and this makes it more difficult to weigh accurately).

I hope you can get this sorted!