Does co2 induced ph change impact breeding aspito ?

[anewbie]

I'm curious if the ph reduction caused by adding co2 would make for viable breeding of apisto that require lower ph. My inclination is no since co2 doesn't actually make the water more acidic - at least that is what i've been told - and that is the same reason it doens't impact fish health the same way as moving fishes from ph x to ph x-1 (in my case 7.1 to 6.3-6.4 for my high-tech tanks). I'm not sure if anyone here has actually tested this but if so please comment.

 

[IndianaSam]

CO2 changes your pH, but doesn’t change the other ions in your water so there’s no softening.

 

[anewbie]

CO2 changes your pH, but doesn’t change the other ions in your water so there’s no softening.

But some aspito need low ph for the eggs to hatch at a given hardness so I'm not following. My understanding if my tds is 80 and the ph is 7.2 the eggs won't hatch for nijjensi (for example) but if the ph is 6.4 they will hatch so what has ph to do with softening ?

 

[MacZ]

what has ph to do with softening ?

This:
Carbonate + 2H+ <-> Hydrogencarbonate + H+ <-> carbonic acid <-> CO2/H2O

H+ are Hydronium ions, which are measured in pH. The more the more acidic. KH (Karbonathärte = german for carbonate hardness) is the measurement of carbonates in the water. According to this formula the more CO2, the more carbonic acid, the more H+, the lower the pH. As soon as the CO2 gasses off again when you stop adding it, the pH rises again. So to lower the pH without fluctuations you have to lower KH, otherwise as soon as the CO2 turns off for the night (which it should!) the pH rises. Because the higher the KH the more carbonates, the more H+ you need to balance them out, the more CO2 is needed.
The "<->" means that these reactions are in flux and constantly balancing out.

And that's why people use RO water with low to no KH and peat, botanicals or other means of adding H+ instead of CO2 which tends to gas out unless constantly added. And constantly adding CO2 (even more than plants can use up and carbonates can bind) is detrimental to fish health. They can basically suffocate if the CO2 levels are too high.

While usually pH fluctuations can be quite high in nature and also in fish tanks (look at high-tech planted tanks with CO2-injection), for your situation you want a stable low pH.

 

[anewbie]

Well i wasn't planning on adding co2 to encourage eggs to hatch - but i do have planted tanks that have co2 injection and i was curious what impact it might have on the eggs. I had been told it doens't impact the fishes because acidic nature of the water remains constant. Of course this begs the question - if i put the eggs in a container and leave the co2 on 24 hours (no fishes to suffocate) would the eggs hatch ?
-
From what you said it seems to imply the eggs would hatch if the co2 was left running at night and the kh has little impact on the actual ability of the eggs to hatch or did i misunderstand ?

 

[MacZ]

From what you said it seems to imply the eggs would hatch if the co2 was left running at night and the kh has little impact on the actual ability of the eggs to hatch or did i misunderstand ?

You misunderstood. Depending on the KH you might have to add a lot of CO2. If it's too much for the fish it also is for the eggs. Those also need a good supply of oxygen, which is why the females waving fresh water on the eggs constantly. You might get the pH down, but the hardness is still as before and the CO2 would rise during the night, eventually reaching dangerous levels.

For many Apistogramma the TDS / conductivity is more important anyway, which means the KH will be low anyway, and it will be easier to lower pH with peat and botanicals in that case.

 

[Mike Wise]

Low pH and/or soft water both tend to retard bacterial growth. The eggs of many blackwater species appear more susceptible to bacteria, so low pH was recommended in the past - but not absolutely necessary. If you can keep the eggs in a relatively sterile environment, they should hatch (I have never been successful artificially hatching and raising apistos from eggs). You might find a skewed sex ratio because pH, to a lesser degree than temperature, affects sex determination. Why not experiment with your CO2 and see if it works, and let us know. For me, it is easier to just adjust the water values to suit the fish, but I am a lazy aquarist.

 

[anewbie]

Low pH and/or soft water both tend to retard bacterial growth. The eggs of many blackwater species appear more susceptible to bacteria, so low pH was recommended in the past - but not absolutely necessary. If you can keep the eggs in a relatively sterile environment, they should hatch (I have never been successful artificially hatching and raising apistos from eggs). You might find a skewed sex ratio because pH, to a lesser degree than temperature, affects sex determination. Why not experiment with your CO2 and see if it works, and let us know. For me, it is easier to just adjust the water values to suit the fish, but I am a lazy aquarist.

Well my aspito tank does not have co2 so that is not an easy option. I could try to steal some of my hongsloi eggs and hang them in a high-tech tank but the co2 goes off at night in that tank for fish benefits. So it was largely an academic curiosity. When i leave this condo i might actually try the experiment as well as have access to ro water to soften things up but that isn't going to happen for another 14 months. I think my water is only a bit too hard but not sure - i know the eggs last about 3 or 4 days but eventually she gives up and they don't hatch. I do find it odd that she lays them on the HMF but she done it twice now... and nothing is eating them.