Mbuna tank sudden pH drop

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gilpi

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Scenario... 55g, 14 mbuna two canister filters, tank has been established and stable for years, ammonia is always zero, temp always 78f. Did half tank water change day prior and I have a habit of checking pH after a big WC since I had a pH crash once before right after the WC. So a day after the water change, fish are fine eating well, couple of hours later they are all gasping for air on top, I knew exactly what to check for and sure enough, pH is under 7. Quickly mixed some baking soda in water and kept slowly adding it till the pH reads around 8.2. By now some of the fish are laying in their side and some just floating lifeless on top. Within an hour they all seem to have gotten over the shock but I might still lose a couple. Please someone educate me as to why the drop in pH a day after a WC? By the way, my tap water pH is always around 8.2.
 
Have you checked the pH of the tap water today?
You should check the tap water pH before doing a water change to make sure the water company hasn't done something to it.

A sudden drop in pH doesn't normally cause fish to gasp at the surface.

A sudden drop in pH should cause problems straight away, not 24 hours later and 2 hours after feeding the fish.

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Are you adding carbon dioxide (CO2) to the tank for plants?

Is there aeration in the tank?

What did you feed them?

Do you have any moisturising cream, hand sanitiser, or anything else on your hands that might have washed off into the tank?

Do you have any limestone rocks in the tank?

What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).
 
Anyone using some form of crushed coral in their substrate?
 
Mbuna and African Rift Lake tanks should always have shells, limestone, dead coral rubble or some sort of calcium based substrate and ornaments to help keep the pH up. Limestone and shells are naturally occurring items in Africa's Rift Lakes and are cheap to buy.
 
I definitely need to consider crushed shells and crushed coral in the substrate versus adding chemicals and salts, adding the sodium bicarbonate to the tank was a quick choice I had to take to save the fish. Gotta say the African Cichlids are resilient, going from what I thought was going to be an almost total wipeout to all of them acting like nothing happened in just a matter of two hours.
 
I only ever used crushed limestone for the base medium of my African Cichlid tanks, and never had a pH drop. I would never make big water changes on those tanks, just 25%. You need to be careful if you are going to perform large water changes on tanks.
 
I definitely need to consider crushed shells and crushed coral in the substrate versus adding chemicals and salts, adding the sodium bicarbonate to the tank was a quick choice I had to take to save the fish. Gotta say the African Cichlids are resilient, going from what I thought was going to be an almost total wipeout to all of them acting like nothing happened in just a matter of two hours.

Also consider crushed coral in your filters
I use 1.5 kg of it in my 2 canister

Also ocean rock is good, mine is filled with 25kg of it
 
Look at where African Cichlids come from, they come from limestone filled lakes. Not Coral or the Ocean. These are freshwater fish living in lakes filled with limestone, which is why I fill my tanks with limestone.
 
Look at where African Cichlids come from, they come from limestone filled lakes. Not Coral or the Ocean. These are freshwater fish living in lakes filled with limestone, which is why I fill my tanks with limestone.

Ide love to fill my tank with limestone but I really can’t pull out everything in my tank including fish and change it
 
Limestone, dead coral rubble and shells are all made from calcium carbonate and will work in a Rift Lake tank.
 
Limestone, dead coral rubble and shells are all made from calcium carbonate and will work in a Rift Lake tank.
Limestone has a dead mass component to it unlike the others, which means you can use rainwater and maintain hardness and pH.
 
My problem is I have always been worried to "over pH" the water, is there such thing as too much?
 
Another thing I forgot to mention was, during the pH drop, the water surface was loaded with bubbles. This whole thing was strange, I have been keeping African cichlids for about 15 years, never saw this and it all happened within a couple of hours. The baking soda did the trick, all survived and looking good.
 
Limestone, dead coral rubble and shells are all made from calcium carbonate and will work in a Rift Lake tank.
Do they have a lifespan? In other words, the rocks and crushed coral and shells, do they have to be changed eventually?
 
Do they have a lifespan? In other words, the rocks and crushed coral and shells, do they have to be changed eventually?
I don't know if there are any chemists around here, but if not, I'll hazard a guess. Our local water where I just moved from was kept in unmodified limestone reservoirs dug out 150 years ago. They pretty rapidly hardened the soft river water, and gave it a well buffered pH of 7.4. Based on that, I would say you'd need to change out the limestone every few centuries...
 

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