PH Changes and PNG Rainbows, I'm Confused

I think a lot of fish can adapt to a higher or lower pH or hardness if done slowly. What really stresses fish is a rapid change in pH. Going from 6.8 to 7.8 is a 100 times difference. 6.8 is 100 times more acidic than 7.8 (pH is on a log scale). They point here is to try to keep the pH fairly constant. Many fish can adapt to a different pH than their natural environment but will not be able to tolerate pH swings.

This is my opinion, based on my experience. I've had plants in my tank since set up 10 years ago. I've been using DIY CO2 for at least 5 years and my pH will go from 6.8 in the morning to 7.6 at lights out. I don't have PNG rainbows, but have become convinced that the pH shift from this has had absolutely no effect on my fish. In fact, the healthier my plants have been, the healthier my fish have been (You don't want any rosy barbs do you?). Now I know, if I dropped a chemical in my tank to cause the same kind of pH shift I''m sure all my fish would be floating belly up. I honestly don't believe the pH on its own has any effect on fish or at least it doesn't when it is in a constant state of change like in a planted tank. My experience tells me just what most on the internet tell me. It is the amount of dissolved solids in the water that throw fish for a loop. If you are concerned about going too low, have you considered increasing your kH so the pH will not shift as low to get your desired CO2 level?

On the other hand Have You considered not setting up your CO2 equipment and just sending it to Me

I really don't believe a low (or high) pH level will have any significant effect on fish.

I think consistency is a possible issue for you. I run pressurised using the micro mist method. When I was first trying to tune my CO2 levels it was the Rainbow fish who first let me know when levels were too high even to the point of trying to jump out of the tank. High levels of CO2 can make fish act strangely, not just gasping for air. Using a pressurized tank will allow you to be dead on consistent day after day, the fish IME will adjust, and it will be better for the plants also.

Is your circulation adequate? Dead Spots? Two fifty % water changes a week should eliminate any TDS problems. Good surface water movement?

I get a pH swing of about 1 and that has never ever been an issue with the fish, it is however, a CO2 induced swing.

My plants begin to pearl heavily about two hours into the photo-period so I know O2 levels are very high. Are you seeing good pearling?

Jay

My experience is the same as Canucks. The fish don't care about the pH as long as TDS remains constant. My water will shift from pH 7.6 to 6.5. I've accidentally took is as low as less than 6 and it had no effect on the fish although there must be a point where it's dangerous.

As far as I know, water can be both rich in CO2 and O2 because they are not mutually exclusive.

This may sound counter to what you'd expect but if you have a good plant mass, I would hook up the compressed CO2 and get it running and stable. The plants will produce enough O2 for the fish. If you have a solenoid on the regulator you can switch off CO2 at night (I do) and run an airstone.

Roan Art said:

I have the KH stable at 4 atm, how high is too high?

Roan

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I think you'd have to look and see how high a KH the rainbows could take,but I've seen scales for KH go all the way up to 15 dkh.

I wish I could give you a more definitive answer but I don't know whether you will find one anywhere. I know on the subject of discus you will find successful experts who swear, they have to have perfect pristine conditions and would never dream of keeping them under planted tank conditions. Others have discus that breed in planted tanks with a pH that's too high. (I consider breeding fish a sign of success) I can't say that a swinging pH isn't having a detrimental effect on your fish, maybe you will have to forego the high growth planted tank for a slower growing non-CO2 tank. I don't know the particular of your tanks but normally with a successful CO2 injected high growth tank, the oxygen levels are going to be much higher then any other type of tank. Oxygen and CO2 concentrations are independent of each other, a high CO2 level does not displace oxygen. If your plants normally pearl without the surface agitation, increasing the disturbance is actually going to lower your oxygen levels, (to closer to the atmospheric equilibrium level).

As I pointed out before, all I can share is my experiences and I admit I don't have any with your type of fish. One thing I wondered about in reading your post though is that if they originate from waters with higher pH, I would have thought they would have a higher gH and kH then 4 (degrees, I assume). I would consider 4 at the low end of moderately hard water.

Hope 4 your sake a rainbow expert chimes in. The only problem being, you will find experts that have had success by just about any means you can imagine to raise fish. Which will leave you right where you started from, experimenting until you find a method that brings you success. Ain't aquaria fun :duh:

Fish do not and cannot "read" pH. The horror stories of "pH shock" (no such critter) are in fact osmotic shock (osmolarity is very important to fish - they must adjust their physiology when the water differs significantly in osmotic pressure) to manitain their internal chemistry in a stable state. The pH changes from CO2 do not affect the osmotic pressure of the water significantly. If you have TDS equipment you can check this for yourself.

Many rainbowfish are quite sensitive to oxygenation, but I have never seen any sensitivity to CO2 supplement, up to at least 30ppm CO2. Do you have a trap bottle or wash bottle between the generator/fermenter and the tank? I would be much more concerned with getting liquid fermrentation products into the tank than the CO2 itself.