Question about pressurised CO2 and water disturbance

[amateurfishkeeper]

So I'm just wondering about this new CO2 set up I'm using. Can anyone clarify this doubt I have. If I have a spray bar returning water into the tank from an external filter is it true that it shouldn't create any water disturbance on the surface of the water? In other words, should I be angling the returned water into the water under the surface so that the surface of the water is completely still? If there is disturbance will it mean that I'm driving off the CO2 that is being added by the pressurised system? And if that's the case and I'm not using any type of airstone, does it mean that I'm only relying on oxygen for the fish from the plants? I've lost a ram and six discus so far since adding the CO2 system so I'm a bit worried that this foray into CO2 is incompatible with keep fish. It would be useful to know about the CO2 / fish / oxygen balance if anyone can help. Thanks a lot!

 

[ajm83]

ardjuna did a good post about this here.

Without surface rippling your CO2 levels can increase up to some dangerous levels later at the light cycle (up to 80 ppm in my case). When you add rippling, your CO2 level will be somewhat lower, but at the same time more stable and constant during the whole photoperiod (40 ppm).

Also if you use for example 1 bps, the increase of CO2 concentration will be slower (more shallow) then in case you use 3 bps → in that case the increase will be steeper (like on the picture).

So what you want is:
1) More bps for quick increase of CO2 level to the desired level (for example, at 1 bps your CO2 gets to 30 ppm after 4 hours, while at 3 bps you achieve the same level in 2 hours).
2) Surface rippling for maintaining the uniform/stable/balanced CO2 level during the whole photoperiod.

PS: As you can see from the picture, aeration (using air stones) is not as effective as surface rippling.

 

[Julian]

Long story short, you need surface agitation to disperse CO2 else it will build up and kill everything. Then you need to add enough CO2 so that you can maintain it at 30ppm.

Just raise your spray bar/lilly pipe until you have some surface agitation, then adjust your CO2 accordingly.

 

[Jose]

Long story short, you need surface agitation to disperse CO2 else it will build up and kill everything. Then you need to add enough CO2 so that you can maintain it at 30ppm.

Just raise your spray bar/lilly pipe until you have some surface agitation, then adjust your CO2 accordingly.

I agree with this, though i have to say its not the only way out there. Others like ADA and many famous aquascapers go for no surface agitation. But they do aerate the tank at night. Its harder to get your co2 constant this way and it normally keeps climbing through the photoperiod. I believe this is how they can get away with aparently adding quite little co2. There is also the filter variable to complicate things further , i.e if it degasses co2 and adds O2.

 

[Andy Thurston]

I agree with this, though i have to say its not the only way out there. Others like ADA and many famous aquascapers go for no surface agitation. But they do aerate the tank at night. Its harder to get your co2 constant this way and it normally keeps climbing through the photoperiod. I believe this is how they can get away with aparently adding quite little co2. There is also the filter variable to complicate things further , i.e if it degasses co2 and adds O2.

decent regulator and needle valve solves this climbing problem.
also some ADA style tanks (no surface agitation) have an airstone running at night

 

[Jose]

decent regulator and needle valve solves this climbing problem.

I dont think this is totally true. Even with a good needle valve the co2 will keep climbing (through the photoperiod) if offgassing is not strong enough. Its more about CO2 gradient, imput of co2 and output.Basically both methods will level off at some point. But w/o surface movement the "equilibrium" will be reached after a long time (maybe two days sometimes), yet if there is some surface ripple the stability will be reached sooner (T. Barr recommends around 40 minutes if your diffusion method is good enough). Look at the graphs shown and youll see that w/o surface movement there is a tendency to level off but one photoperiod is not enough time. Also other things have a huge impact w/o ripple like surface scum.

But I dont think this is of any help for people starting with co2. As I said follow the first advices and keep some surface ripple.

 

[amateurfishkeeper]

Thanks for the responses!

I'm new to using CO2 and I'm trying to learn more as I'm going along. I don't have a PhD in botany or biochemistry or anything like that so you'll have to forgive my ignorance. I haven't memorised the genome sequences of plants etc .. you get the picture lol.

So far my observations have been that the use of Co2 has killed some fish and that's undoubtedly my fault. So I've tried to lower the amount of CO2 going into the tank. I pay attention to what the drop checker is telling me etc. I pay a lot of attention to what the fish are telling me. This is my first week of using EI and I've got massive flow in the tank which looks very well circulated - fast flowing hillstream etc. I assume the EI dosing is of some benefit but awaiting results on that . I'm trying to pick up on best practice from people who seem to know what they are talking about but also trying to develop my own instincts based on observation and experience. So I'll keep the water disturbance going in combination with closer control of the amount of CO2 going into the tank. I did have very vigorous plant growth before using CO2 but not in all species. Some just wouldn't develop at all in line with what people say about certain species. I guess it was the failure of these early planted species to grow that got me into the idea of CO2 use in the first place. So I guess it's all about finding that sweet spot or combination of factors that just somehow works. It's not about spending massive amounts of cash I guess but finding what is right for your tank. I appreciate everyone's input!!

 

[Jose]

Thanks for the responses!

I'm new to using CO2 and I'm trying to learn more as I'm going along. I don't have a PhD in botany or biochemistry or anything like that so you'll have to forgive my ignorance. I haven't memorised the genome sequences of plants etc .. you get the picture lol.

So far my observations have been that the use of Co2 has killed some fish and that's undoubtedly my fault. So I've tried to lower the amount of CO2 going into the tank. I pay attention to what the drop checker is telling me etc. I pay a lot of attention to what the fish are telling me. This is my first week of using EI and I've got massive flow in the tank which looks very well circulated - fast flowing hillstream etc. I assume the EI dosing is of some benefit but awaiting results on that . I'm trying to pick up on best practice from people who seem to know what they are talking about but also trying to develop my own instincts based on observation and experience. So I'll keep the water disturbance going in combination with closer control of the amount of CO2 going into the tank. I did have very vigorous plant growth before using CO2 but not in all species. Some just wouldn't develop at all in line with what people say about certain species. I guess it was the failure of these early planted species to grow that got me into the idea of CO2 use in the first place. So I guess it's all about finding that sweet spot or combination of factors that just somehow works. It's not about spending massive amounts of cash I guess but finding what is right for your tank. I appreciate everyone's input!!

I would get a cheap (£10?) pH pen from ebay or whatever you can afford and monitor co2 via pH. Leave it hanging from your tank. You are aiming for a 1 unit pH drop which is aprox equivalent to 30 ppms of co2 no matter what water you have. This is an almost instant read whilst your drop checker takes at least an hour. Its also more accurate IMO. Dont worry about the chemistry, its all been put down in simple words already.

 

[amateurfishkeeper]

Thanks Jose - a great idea but sorry what does 'aiming for a 1 unit PH drop' mean?

 

[Julian]

If your pH is 7.8, when your lights come on your pH needs to be 6.8 to give you 30ppm of co2.

 

[amateurfishkeeper]

Forgive me ignorance also but if the PH pen gives me a PH reading how does that correlate to CO2 levels? Is there a table to calculate it?

 

[amateurfishkeeper]

Sorry you answered the question. Cheers!!

 

[JamieB]

Is there a good way to get surface disturbance without upsetting low flow fish, for example bettas? I use a sponge over my output and it does disturb the water surface but no where near the amount I'd imagine is required...

 

[Jose]

Thanks Jose - a great idea but sorry what does 'aiming for a 1 unit PH drop' mean?

Good question.

Normally people have their co2 on a timer so that its off at night and turns on an hour/or two before lights turn on. You should measure pH in the morning after all the co2 has escaped from the tank (you need goo aeration at night for all the co2 to "evaporate"). Lets say this measures a pH of 7.5 in the morning. Then you start adding co2 and after a couple of hours your pH should be around 6.5 (at this point lights turn on) and ideally it would stay there for the rest of the photoperiod. So like this example:

12:00 (pH=7.5) ->CO2 turns on
14:00 (pH=6.5)-> Lights turn on
.
.
.
20:00 Turn CO2 off
21:00 Turn lights off

You should take pH measurement every time you can and make sure there is a 1 unit pH "drop" through the photoperiod.

 

[Jose]

Forgive me ignorance also but if the PH pen gives me a PH reading how does that correlate to CO2 levels? Is there a table to calculate it?

Yes. the table is the pH Kh table.
http://www.barrreport.com/forum/barr-report/co2-enrichment/11862-co2-ph-kh-table

But the kH is independent here.

 

[amateurfishkeeper]

OK I see. The 'drop' refers to the change in the PH over time. By the way, is that example schedule the one you use? I have a timer and have the Co2 coming on one hour before the lights come on at 8am. The CO2 goes off an hour before the lights go out at 4pm (8 hour continual photoperiod). Is that the right kind of approach or am I making some kind of terrible mistake? Perhaps I need the lights to come on later like in your example?

 

[Jose]

OK I see. The 'drop' refers to the change in the PH over time. By the way, is that example schedule the one you use? I have a timer and have the Co2 coming on one hour before the lights come on at 8am. The CO2 goes off an hour before the lights go out at 4pm (8 hour continual photoperiod). Is that the right kind of approach or am I making some kind of terrible mistake? Perhaps I need the lights to come on later like in your example?

It could be that you need your lights to come on later but I dont know until you measure your pH at different times. I would keep a photoperiod at first of around 6 hours, 7 tops.

 

[5678]

Some interesting information in this thread.

My water is quite hard with a KH of ~15/16 (and PH of 7.9/8.0) if I have understood things correctly, this will mask the PH drop even with the desired level of co2?

From looking at that table I should only be getting a PH drop to around 7.3 rather than the full 1PH that gets mentioned by default? If that is correct, what colour would that translate to in a drop checker?

 

[ian_m]

If your water is pH of 8 then after two hours of CO2 hopefully a pH of 7 should be about 30ppm CO2 (it won't see below). A drop of one unit pH regardless of initial KH value.

Clearly this is approximate as there is clearly something else in your water adding to KH and/or altering pH, as reading at the end of the table in Toms link, 16KH water with no CO2 will have a pH of greater than 8.6 and yours isn't.

At 30ppm the drop checker should be green, however with your water and 1pH drop, I doubt it will be as green, maybe in 20ppm region as there is something else in your water affecting pH/KH.

See drop checkers here. I highly recommend the JBL one, shown below, as easy peasy to read the colour against the white strip, unlike the stupid breakable, but cool look, but a b**ger to read glass drop shaped ones.
http://www.ukaps.org/index.php?page=co2-measurement-using-a-drop-checker

The great advantage a drop checker has is it is isolated from the tank water and only reads the gas level in the water regardless of pH, salt levels and other contaminants of your tank water. Disadvantage is can take an hour or more to read, meanwhile you have gassed your fish.

 

[Jose]

From looking at that table I should only be getting a PH drop to around 7.3 rather than the full 1PH that gets mentioned by default? If that is correct, what colour would that translate to in a drop checker?

There are a few things going on here.

From looking at that table I should only be getting a PH drop to around 7.3 rather than the full 1PH that gets mentioned by default?

Do a search for this topic its not a simple one. But in the end your kH measurement has errors, thats just how they are, because they measure "alkalinity" as a whole not only kh. So if you use your kH to determine your co2 then you will always have less co2 than you expect. Its the same if you use the kH from your water supplier, in the sense that it changes during the year. This is why we take out the kH variable. It has been found that a pH drop of 1/1.2 normally correlates with 30 ppms of co2 independent of your water hardness. It doesnt even matter if you have an acid in the water because this will affect the initial ph but not the absolute "ph drop".This can be proven with the table if you could know your co2 ppm at the equilibrium with air. This is hard to grab at first. Always look at your fish for any sign of distress and change co2 very slowly.

If that is correct, what colour would that translate to in a drop checker?

This is the problem with drop checkers that the coulour changes are very subtle. So from 15 to 30 ppm you might not be able to tell the difference. Plus it tells you the co2 there was 3 hours before plus co2 bubbles could influence the reading etc etc.