Pressurised CO2

Just bought the new Hydor Pressurised Co2 kit in Wackers on Thursday, Everything is running fine but i have one question for those of you that might use it or have a pressurised Co2 kit of your own.

Do you manually switch off your Co2 at night and reset it every morning or do you leave it running and have an airstone running with it at night. Its just a pain in the a*se having to get the right amount of bubbles per minute set every morning.

I've been reading a lot of contradicting views about running Co2 at night without an airstone. Any ideas?

Hi Peter, i have mine running through my light timer with a solenoid switch, saves hassle of setting it every day.
Mike

I'm running an airstone at night and everything seems to be going fine.

My Ph seems to have dropped slightly from 7.2 to 7.0 in about 5 days but i'm keeping an eye on my fish and they are all happy as larry.

Can't wait to start seeing some results with my plants.

Hello peter, you will need a solenoid valve(electro magnetic valve) for your Co2 to switch off automatically at night.
Doing this manually is just not practical and as you puy it "a pain in the a*se".
You can plug the solenoid in to a timer with your lights so when your lights come on or go off the Co2 will do the same.

If you do a ph test at the end of your light period and again just before lights on the next morning you will then see the difrence in ph. It is not unusual for this to change by a full degree of ph. e.g.( 6.5-7.5)

You can use the airstone at night but this will drive off the Co2 if used during the day.
Some people use an airstone lightly all the time and just compansate by adding more Co2. This is something i am trying myself at the moment but it is still early days for me to comment.

You probably know this already, but just in case you don't...

You definitely need a KH test kit too so you can correlate your pH and KH to find out your dissolved CO2. Once you have pH and KH you can check somewhere like Chuck's calculator and see where you are on the CO2 chart for morning and evening. You have to play it safe and I would definitely be aiming for c.20ppm at the highest concentration of the day.

A very good way of being sure you are not overdosing is to get a cheap pH controller . Plug it into a timer so it can only operate during your photoperiod. It will operate your solenoid based on a target pH level. I have one of these and it gives great peace of mind, especially since before I had it I somehow managed to overdose my tank and lose 8 fish.

I think the reason why my tank was overdosed is because of an unexpected change in KH from 4.5deg to >7deg after a water change. Anything you add to your tank can potentially have an effect on KH so do KH tests until you know the effect of every additive/wc. I wish I had an RO unit so I could manufacture water with an exact KH/GH, also allowing me to target lower KH to get more acidity for amazonian fauna.

Sorry for the long post, but I just want you to know that CO2 is great until you overdose your tank!

Cheers Will,

I have been keeping an eye on KH and Ph and when i checked it against a chart i had between 15-20 ppm of Co2 which sounds just about right.

I'm gonna do some readings at just before lights off and before lights on and see what that turns up.

I am happy my Ph has dropped as i have tetras and have future plans for discus, but the fluctuations that occur while dosing Co2 are worrying? A drop/or rise of 1 unit in the space of a day cannot be good for the fish (and plants???).

I will get a solenoid valve sooner rather than later, any ideas where i can get one and rough prices?

Here's a couple from a company I have used very successfully in the UK:

D&D Solenoid

JBL Solenoid

If budget is an issue you could probably find a much cheaper equivalent on eBay!

Checked Ph before lights out last night and after lights on this morning.

Kh has remained at 3 and Ph was roughly 6.6-6.8 on both occasions.

The Water seems to be stable, i'll be doing a water change this evening, my tapwater is about 7.2 so it will be interesting to see what effect a 15-20% water change has on the tank.

I'll keep you all posted.

P.S All fish are doing great and my Large Black Widow Tetra is about to drop a heap of eggs. If only i had a spare tank set up!!!!!

If you have an average size tank (20-60 US gallons) and use less than 2 watts per gallon then 15-20 ppm of CO2 is about right, if you use 2+ WPG then current thinking would suggest aiming for 30ppm CO2 as the minimum you should aim for, otherwise you will experience algae problems.

The problem with the CO2 charts is that they assume a base level of 3ppm CO2, and this is an inaccurate assumption, but this is the baseline the charts work from, they assume that a degassed sample of water will contain 3ppm CO2, but in reality a degassed sample of water (degassed=water that has been let sit for 24 hours) could contain anything from 0.5 to 3ppm CO2, and if you start at the lower baseline your figures will be totally different when using the KH/PH relationship and cross referencing it on a chart, and therefore "you may or may not" be adding the correct amount of CO2.

Basically the CO2 charts are flawed.

Hay zig, good to see you back on the forum.
Do you know of an alternative way of mesuring the Co2 in a tank rather than using one of the charts.

Hay zig, good to see you back on the forum.
Do you know of an alternative way of mesuring the Co2 in a tank rather than using one of the charts.

Thanks platty252

There is no real definitive answer here tbh, basically there are a lot of variables at work, probably too many for the answer to be straightforward.

Like a lot of things in this hobby some things just seem to be accepted as fact for a long time until we auctually start to analyse them, the CO2 charts that we as hobbyists use seem to fall into this catagory and have been accepted as "fact" for a long time (they are still accepted as fact by most people in the hobby today and lots of CO2 charts are out there all based on the same flawed origional) Nobody is really sure where the CO2 chart that we use today in the aquarium hobby came or eminated from, they probably started to be used in the current fashion around the early 1990's, somebody probably came up with a theory that was generally accepted at the time as being a reasonable method to measure CO2 levels and with the advent of the internet this theory just got carried along into the hobby and hey presto the CO2 charts are still accepted today as being correct.

The basic premise of the PH/KH, CO2 relationship is based upon no other acids being present in our water except carbonic acid from the addition of CO2, now this situation is unlikely as our aquarium water will typically have some other buffer/s present, there could be organic or humic acids (usually from the substrate) tannic acids (from driftwood, bogwood) phosphates, any of these could be present in the water and these all will act as buffers and throw the CO2 levels off and make our measurements inaccurate. The effect of other buffers being present will give you false readings for CO2 levels.

There are other more basic problems with the charts as well, as i said in the origional post the charts assume a starting position of 3ppm CO2, this is based upon a degassed sample of water being in equilibrium with the CO2 in the atmosphere at 3ppm, but in reality the CO2 in any given sample of water could be anywhere between 0.5 to 4ppm CO2, so basically where do we start our measurement, this is the problem, and neither KH or PH will tell us this. The other problem of not knowing the correct starting point for our measurement of CO2 is the Ph part of the relationship, Ph is based or measured on a logarithmic scale, a 1 drop in ph is 10x, a 2 drop is 100x and so forth, so when we use a logarithmic scale for measurement (as in the ph/kh measurement) it is vitally importment that we have an accurate starting point, as a measurement of say 10x3ppm is very different to a measurement 10x0.5ppm. So this is really the root problems of the CO2 charts they do not give accurate measurements of CO2 levels.

A good starting point for measuring CO2 levels for highlight tanks to achieve 30ppm is to take a sample of your tankwater and let it sit for 24 hours, you then measure the ph of this water (how accurate is your ph kit, yet another variable when using the PH/KH chart method) anyway measure the ph and then use this as your baseline, so if the measurement is say ph 7, aim for ph 6 in the tankwater when you inject the CO2, you want to aim for a full unit of ph below what the reading of the sample tankwater has given you, this method is "reasonably" accurate and a good starting point, to work out other ppm's of CO2 you would need to do some math taking into account the logartithmic nature of ph.

Long winded answer but thats the way of it!!

That makes sense.
I will test this during the week to see what mesurment of Co2 i get compered to what i am getting at the moment.

I know what you mean by the ph test kits. I had 3 diffrent brands tested against each other and they were all off. They dident even match each other.
I will stick to my ph meter.

I should mention that i finaly got over my phosphate problem after 4 1/2 months and no algie in sight. At long last.