Co2 confusion

[Husmut]

The situation...Been keeping planted tanks for some time with the use of nutrients/trace elements and good light with reasonable success. Recently I decided to try DIY Co2 on my 90ish gallon tank, knowing that it would have to be a pretty special unit if it was to supply a tank this big. So, off to the drawing board and; my attempt seems to have been successful.....I think! It comprises of two 3.5 litre pressure garden sprayers (You know the type that spray weed killer) that had nossels that accepted my tubing easily. This was then fed into an "inline" garden hose filter which is connected to a very compact 700lph pump. I just put some corse sponge in the filter and, after the initial observation of bubbles reaching the surface, connected some large clear hose to the other end to extend the contact time of the bubbles before leaving the "reactor". All good!
The problem....... I know that there is a direct relationship between Ph and Kh, so I buffered the water and waited for my Ph to drop to around 6.8 as it is at 7.8 at the moment (which is unusual in itself)......but nothing, not even a small move! It has been nearly four days bubbling very nicely at a huge rate and the Kh is at 6d but the Ph wont budge! Is this a direct relationship to the large volume of water and I am just being impatient? I have done every thing I can think of including sealing my trickle filter. Is there a problem I am missing or is it a matter of giving it more time?

 

[greenmaji]

your target ph sounds good for the kh level you have.. I think you might want to look into getting or DIYing a reactor for all that nice CO2 your getting... you shouldnt have surface bubbles of CO2 it would just be leaving the water.... wet/dry trickle filters can be a small problem as well.. I ran a thread on that subject...
Ive never heard this garden sprayers idea.. I like it.. make sure you dont have any leaks and how long is your runs of CO2 line? do you have a trap to catch liquids and solids in the line?

 

[hashbaz]

I know that there is a direct relationship between Ph and Kh, so I buffered the water and...

What do you mean by "buffered" the water?

If you buffered with carbonates (like baking soda) everything is OK, but if you buffered with something other than carbonates, this could be your problem.

I am a little confused on how your reactor is set up. Ideally there will not be any bubbles leaving the reactor.

 

[Husmut]

Greenmagi: Lines are about 2.5 meters including short runs of line from the bottles to the "T" joiner. I have noting cathing solids but I do have a check valve inside the reactor just above the air stone. By reactor, you do mean a device that mix the bubbles with water? The system has not been up long enough for solids to be a problem tho! Sound ok?

Hashbaz: You could of been onto something here. I did buffer the water with a carbonate generator but about a week before setting up the Co2, I put some 9mm "river" stones that I have since removed as this could be the source of my woes! I did this just after posting original thread but there is still no change. I suppose I need to be more paitent. Will let you know.

Thanks guys! Great site!

 

[greenmaji]

I like this design.. yours of course is bigger.. you could adapt the ideas though..
http://www.qsl.net/w2wdx/aquaria/diyco2.html
there reactor is a in the tank thing and has no bio-balls.. I prefer a reactor thats inline with my canister and has bio-balls to help break the gas up... they have a "gas separator" in there project to catch liquids and solids.. that might be a good idea for your system before it becomes a problem.. I think it would solve the white stringy problem that alot of users on here are having as well..
Have you tested your KH? testing your KH of your source water, ie tap if thats what your using. would help as well..
Im guessing you couldnt fit the garden sprayers under the tank or you wouldnt have so much line... I would suggest to try to shorten that distance if possible.
do you have the plans you used for your system... how you designed your reactor? there might be a engineering problem that you didnt foresee.. how far down into the garden hose filter is the airstone?

 

[Husmut]

Thanks for the link! Funnily enough it is very close to my setup, but it was good to see a "working" design. My reactor sits in the tank also, though I am concerned it maybe to small. Is this a consideration? I guess as long as it is dissolving all the gas, then it does'nt matter, which it seems to be doing. It is only 7 inchs or so tall, but as I have mentioned, I have extended it to the aquarium floor by attaching clear pipe from the outlet. Make sense? I figured this would increase contact time with the water. And, because the garden filter/reactor is fluted to a small hole at either end I am hoping that there is also a fair bit of turbulance in there. My airstone sits about halve way but can easily be moved, even itnto the extension I guess.

The Kh of my tap water is 2d and the ph is 6.8. As mentioned, I have buffered to 6d, but my ph is at 7.8. I have recently noticed some of the plants expiring oxygen this evening so some is atleast getting in there, but the ph wont budge. Would you know how long I would need to wait before an effect to the ph was noticed through crappy tests in a tank this size? Even if I have inadvertantly introduced something that brought the ph up through using those stones( which have mostly been removed for the purpose of this experiment), would the carbonic acid eventually over ride it? I suppose what I am asking is, does the resulting acid by-product of Co2 build up in your tank over time?

 

[mattrox]

You are trying to strike a balance of CO2 in with the amount plants use and the amount you lose through the water's surface. If you plants are getting enough CO2 then don't worry too much about the ph. Just try to keep it constant.

 

[greenmaji]

how long have you had it running? waiting might be needed to see any change..
It sounds like you might have done a little more buffering up your dKH than you might have needed, it might have raised your PH a little too much.. A small pwc might help..
Your right it really doesnt matter if your gass is getting dissolved.. if you have some plants pearling thats definitely a good sigh by the way.. if your test results are accurate on your tank your CO2 levels should be a little low though.. It really depends on how much light wpg you have, if you have 1.5wpg you wont need as much CO2 then if you had say 3.0 watts per gallon..