Freshwater pH...Should I try to lower it?

[parl0017]

Here's my long question.... As a new FK, I'm finding out just how much there is to it. I currently have a 20-long with 2 fantail goldfish that are doing well and seem happy. My other 20-long has 5 Glofish tetras, again seemingly happy, but that's where it ends. I first tried to add 5 kuhli loaches to the tank. I read up on them and waited 1 month after the tank had finished cycling to add them, but 4 of them died within the first few weeks. The last loach is still doing fine, though is very shy since I haven't wanted to get more til I can figure out what went wrong. I then ended up with 7 juvenile albino cories that my sister had just purchased. Since I couldn't put them in with the goldfish, off they went to the Glofish tank where all but 2 died over the next couple weeks. My long-winded story is ultimately about the importance of pH because the tank is cycled at 0, 0, and 10. However, my tap water is very hard with a pH of around 8.4. I've talked to many people about this possibly being the cause of death and while 50% say "absolutely", the other half says "absolutely not". I brought up the possibility at 2 different LFS and both looked at me like I was an idiot. But if pH is not at all important, why am I wasting money to test it!!! I briefly tried peat granules in my filter and my pH plummeted to 6 in about 2 hours! Shockingly, I didn't lose a single fish, but that experience made me very wary about messing with the pH, especially knowing I'll have to deal with it every week during water changes. At this point, I'm wondering if I should surrender the loach and cories I have left and just stick with the Glofish and Fantails! I don't want to buy/add fish if there's a decent chance I'll kill them and it's not fair to them to not have a good-sized school :-(Any advice would be much appreciated!

 

[Caliban07]

Hi Parl0017

The answer to your question lies in the context of the ph drop. If a strong acid (sulfuric) is changing the ph then problems with toxicity will occur and the ph falls. If a weak acid (carbonic, tannic) is changing the ph then little problems occur. It has been proven many times over that fish go through wild diurnal ph changes without any noticeable effect. Many planted tank keepers in fact demonstrate this on a daily basis many at least experiencing a 1 unit ph drop in a couple of hours due to the addition of carbonic acid via carbon dioxide injection. It's not surprising that your fish shown no signs of distress when the ph dropped by 2 units in 2 hours. This would have been caused by tannic acid release from the peat granules.

Fish have a low tolerance to changes in internal blood ph just as we do but have the ability to regulate blood ph too maintain homeostasis. This can be achieved through kidney excretion, respiration and by releasing buffers into the bloodstream.

Ph is just a ratio and tells us little about amounts. If I have a ph of 7 it would mean the the number of H+ ions and OH ions are in equilibrium but the equilibrium could be 1:1 100:100 or 1000:1000. This is why it is important to know and understand the other two parameters that haven't been measured. KH and GH.

KH (carbonate hardness) tells us how likely the pH will change due the the addition of H+ ions. High KH means more H+ ions to change ph and vice versa. Changes to ph in high KH water reflect larger changes to water chemistry and changes to ph in low KH water reflect low changes to water chemistry.

It is the salts and minerals that contribute towards the KH and GH that can have significant effects on fish due to their constant need to regulate the bodies osmotic pressure. Again the fish have means to do this without problems but rapid fluctuations can cause harm.

If you have a ph of 8.4 then you most likely have high KH and GH. There is nothing wrong with this and people have kept many different kinds of fish in water like yours, including Rams, discus and cories without any problems although people do report difficulties breeding fish in waters not suited to their natural environment.

There are dozens of reasons your fish might have died. But because of the regurgitated myths about fish and ph and the fact that ph is so easy to test for its easy to associate your fish deaths with ph. Grab a TDS meter and measure the water your LFS is keeping the cories in then check against yours for example. The fish may have been sick to begin with. Ph most likely has little to do with it.

I keep ottos, shrimp and swordtails in water that fluctuates daily from a ph of about 7.5 to as low as 6.3 and have yet to lose a fish or shrimp whilst doing so.

Hope you have better luck soon.


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[parl0017]

I'm seriously having an "ah-ha" moment remembering myself sitting in chemistry going "when am I ever going to need this information again!" I have purchased a TDS tester, but I had to have it shipped, so I will test my tap water and the store's when I get it. I can say though, I know my tap water is hard. At one point I had some test strips and I live in an apartment that doesn't use a water softener. Thank you for taking the time to give me such a thorough explanation!

 

[Caliban07]

I'm seriously having an "ah-ha" moment remembering myself sitting in chemistry going "when am I ever going to need this information again!" I have purchased a TDS tester, but I had to have it shipped, so I will test my tap water and the store's when I get it. I can say though, I know my tap water is hard. At one point I had some test strips and I live in an apartment that doesn't use a water softener. Thank you for taking the time to give me such a thorough explanation!

No problem. You can cut your tap water with some RODI if you would like to bring the hardness down somewhat. Just another option.


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[Caliban07]

It's also a good thing that your apartments don't use softeners because for a fish tank this is not ideal. The idea of a softener is to replace the hard water elements like magnesium and calcium in favour of sodium to stop staining and limescale build up. They do this at a ratio of about 3:1 in favour of sodium. So because TDS meters measure conductivity in the water lots of Na+ equals higher TDS.

Because TDS meters measure conductivity it will not measure other non charge dissolved solids so the measurement is skewed ever so slightly. True TDS reading involves evaporation and weighing however the trusty TDS meter is probably the most accurate tool we have in the hobby grade testing game.


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