The begining of CO2 injection is harmfull?

go slowly and test

We expect that DIY will not get too much CO2 in the tank, but I've still seen it done with too large generators and too much yeast. So, start slow, then make improvements as you get it all working.

It does take some time for the fish to adjust, I believe their blood chemistry has to actually adapt to the changes. Generally, you just want to go slowly. Typically, with a DIY system and a pH of 8.0, which I assume means a KH of 9 or better, you will not be able to get into a danger zone.

Still, to be safe, don't over do the mix at the start. After everything is running smoothly, test the pH and KH and check a Co2 chart to see if you are near the target 25 ppm of CO2. While you are looking at the chart, determine the minimum pH that is wise, so that you will know that, for example, if you pH goes to 6.6 you have too much CO2, as well as the target pH you are hoping to get.

As you go along, you will try to improve the initial rate and the lifespan of the mixture, as well as reduce the surface losses due to agitation and improve the efficency of the CO2 absorbtion.

Best to start it on a day when you have time to watch the fish for stress, and to be sure nothing foams up and into the tank. So, not too late at night, start on a day when you'll be around. If you are concerned that the rate may be high and the fish may be stressed by morning, add an airstone overnight and remove in the morning when you can watch.

In my experience, Ph changes don't seem to bother fish IF There is little or no change in TDS levels in the tank. This is one of the blessings of CO2. It decreases the Ph but does not effect solids levels or hardness levels rapidly. I have dropped my Ph from 7.8- 6.8 rapidly on many occasions, and have never seen an adverse effect with any of my fish shrimp or snails. furthermore, I run my Co2 24 hours a day, so the level climbs at night and drops in the daytime. This seems to have no effect, and at the same time, many folks who use solenoids without a ph controller have the opposite effect. Co2 lowers at night and increases at lights on in the morning. As long as KH, Gh stay steady the fish don't seem to care.

The true danger with rapidly changing Ph is osmotic shock, and solids in the water are what effect osmoregulation, not the actual Ph. As a general rule, Ph changes are created by Kh changes, and thus they go hand in hand.
CO2 is the exception to that rule so much so that we can calculate Co2 levels by comparing ph to Kh.

There are of course limits to how big of a fluctuation a fish can and will take without stress, but those limits are much wider than most folks believe. And would largely be from water so acidic that it actually burnt a fish gills, not from speed at which the change of Ph took place in the tank.
Dave

I don't turn my c02 off at night, because I can't, but I do run my airwand after lights out and turn it off in the mornings when I turn the lights back on just to be on the safe side.

Good luck!

You must have something leeching into the water. 9 is too high for most fish. You need to get it down. Do a water change until you can find what`s causing it.


The only thing you`ve done is add diy co2?

World Health Organization and Environmental Protection Agency guidelines says that drinking water should not exceed 8.5 pH. 9.0 is a bit odd ESPECIALLY if you have only a 5 KH. Something is not right with your test kit or something.

If I understand it correctly, co2 and o2 don't compete for space in the water column. That's really a flinstones way to put it, but even with high co2 there should not be a problem with o2. Additionally the o2 produced by plants is 100% pure, so as compared to air it does a much better job of saturating the water and reaching max o2 levels. So in theory a high co2 tank with optimum growth will also be a high o2 tank with optimum oxygen levels. I have no surface disturbace at all, and add no oxygen in any way but the plants. I run High Co2, and have tall tanks. I have never seen any symptom of oxygen defeciency in any of my tanks. A couple of these tanks have obscenely large bio-loads as well (guppy breeder tanks with uncontrollable populations)

As far as too much Co2, there is a chart which I cannot find a link for right now, but I believe it is linked in the fertilizer sticky at the top of the plant forum. It shows how to compare Kh to Ph to calculate Co2 levels, and gives some basic (conservative) guidelines to what levels are acceptable.
Dave