Hi all, I've posted a couple times about co2 and had some really top answers so far so hopefully you can aid me again.
I've a 60litre tank,medium to full packed with plants such as HC, rotala bonsai, vivipara, Cryptocoryne lutea. Quite slow growing a lot of them.
I was told to set an initial rate for co2 which I did. 2bps and see how long it took for the co2 to drop say 0.5 of a unit. I did so and set my timer for 2.5 hours before lights on.
I bought a decent ph pen and took the readings throughout the day. My initial ph was 7.3 before any co2 was added. It only dropped to 6.8/6.7 I think at this rate at its lowest.
Since then I've tweaked co2 and left it for day to observe unit drops. It's took me about a week to get a 1unit drop but it's a rate of 4bps. As I've read this is a lot of co2 for my tank.
I have good flow using a fluval 305 canister filter at its highest flow rate as it's connected to a inline heater and inline atomiser so I figured flow rate would have slowed to what's said on manual. I can visibly see co2 reach bottom of tank and work in a circular movement around tank.
I just want to know wether there's something a miss with what I'm doing with amount of co2 added as I'm worried this much is going to affect my livestock when I add them in couple weeks.
I took my kh and gh readings to see what the buffering was like within tank water
The kh took 12 drops and gh took a whopping 23 drops of solution to change the colour needed. Could this be affecting my limited drop in ph?
Can I run at this rate of bubbles or lower it?
I just feel that if I'm throwing too much co2 at my tank for no reason then I'd like to know so I can make a change before livestock is added.
Cheers
Hello,
If you review many of the threads regarding this issue you will normally see that the advice is that it may not be necessary to drop the pH a full unit when the water's alkalinity is measure to be 12 dkH. Hobbyists who don't have the whole picture may sometimes conclude that the information provided is conflicting, and that's usually because they are attempting to fill in the dots.
So for example, you mention that your KH test kit required 12 drops to change color. Since the kits sometimes differ, can you verify that based on that kit instructions the dKH is indicating 12, or 11? So can you see that merely by not stating exactly what your reading is, that it would be possible to misinterpret what the values actually are and to provide advice that may someday appear to someone else as being contradictory?
Also note that the one can use the pH/KH/CO2 chart to determine the target delta pH, but this loses some of it's relevance if the dKH number (I'll assume 12 in this case) is not 100% due to Calcium Carbonate dissolved in the water. The test kit measures alkalinity. It is incapable of measuring KH.
So if we go to the chart and find where the pH 7.3 column intersects the KH 12 row then it would imply that the water's starting CO2 content is around 18ppm which is unlikely.
Still, we are looking for a "Delta", not an absolute number, so we can simply follow the row to the left and stop at the 45.3ppm red box. Now, 45ppm minus 18ppm is 27ppm, which is a pretty good target. That box intercepts the 6.9pH column, right? So for your 12dKH water a pH drop of 0.4-0.5 can be the target instead of a traditional 1 unit drop. Again, there is some ambiguity because we do not know how much of the dKH value is due to ions that are not CO3 or HCO3.
Will this all seem confusing to some people? Well yes, no doubt. Years from now someone will accuse me of conflicting them terribly? I'll regretfully have to plead guilty.
But the conflict doesn't end there. Suppose the water is actually 12 dKH due to 100% CO3 dissolved in it. Lets say you can successfully reduce your bubble rate, to get a 0.4-0.5 pH drop and a 27ppm CO2. Are all your troubles over? Maybe not.
It may be that you are of Klingon ancestry and that your tank is lit by several megawatts of Atomic powered LED. If so, 27ppm may not be enough.
Suppose your flow rate and distribution were not as good as you thought? 27ppm may not be enough.
There are so many ways to having problems, it's staggering.
The 1 pH unit drop is just a guideline which assumes a much lower dKH and which takes into account the possibility that the starting CO2 concentration level is optimistic in the chart.
Acids in the water corrupt the pH reading and alkaline substances in the water corrupt the dKH reading. That's why we don't use tank water in the DC, remember?
You have to outwit the pH/KH/CO2 chart because it always assume your water only has Carbonate (CO3) dissolved in the water and that there are no other acids except for the Carbonic acid that is reacting with the water and with the Carbonate.
We cannot cover every possible scenario so we just shoot for a nice round number that works
most of the time.
The DC is a good indicator visually so you can try to throttle back on the injection rate so that the yellow goes away, and that should give you the confidence that you will be able to add fish - but it will not necessarily guarantee that the plants will be happy.
Hope this helps...somewhat....
Cheers,
