The Dangers Of Co2

[Katch]

I'm just about to head down the high tech path and wanted to know a little more about not killing my fish.

I have a Dennerle regulator and an Aquamedic solonoid. I hear lots of horror stories where the solonoid has stuck open and ended up killing all the fish.

What can I do to reduce or remove this danger?

Also why would this scenario kill the fish - if you have your rate during the day set to a safe level why would it not stay at safe levels if it gets left on over night?

 

[N0body Of The Goat]

I believe it is all to do with the levels of buffer in your tank water. If you live a in moderaely hard tapwater which you use (eg. gH14; kH 11 for me), the chances of a carbon dioxide disaster are relatively small.

However, if you use soft tapwater or RO purchased from LFS (or your own unit installed at home), the lack of buffering capacity cause a massive rapid pH crash due to saturation levels of [edit]carbonic[/edit] acid.

There may well me more issues, but that is the one that my "science boffin" head sees immediately, without having read anything on the subject to do with fish keeping

 

[PDSimon]

I didn't think the pH was an issue, my pH is 6 and the addition of co2, which should lower the pH more doesn't bother the fish.

I thought the biggest problem was the regulator leaking? too much co2 will kill the fish

 

[SuperColey1]

Post No4 from Tom Bar should reduce your worries here:

http/www.barrreport.com/showthread.php/6837-Buffering-Is-KH-Necessary?p=45445#post45445

This subject has been one of argument for years but has been pretty well dismissed over that time too.

PDSimon - The advice you got less than a month ago on this subject on UKaps was correct and as such is fresh in your mind I should think. I would post the link(s) here to a couple of threads on UKaps if it weren't for their silly 'have to register' stance on viewing most of the forum.

Ph is irrelevant. People worry about Ph going from 7 or 6 and crashing. Most of our south american fish like Tetras are actually in very acidic water in their natural 'blackwater' environment. circa 4. Why is the recommended Ph 7 in an aquarium? Makes no sense when you look at it that way. I remember reading a post from some prominent planted guys on APC where the CO2 user with oKH had his Ph dropping to 3.7 and he wasn't worried in the slightest.

I don't think there is any doubt that something can happen and there is a crash but as to what parameter is the problem it isn't Ph. I wouldn't say it is KH much either. As tom states in the post above. In a non CO2 tank where CO2 is limited then plants will use the KH as carbon source. Reducing the KH down.

If we say 'well thats a slow process over time and therefore it isn't a crash' then explain this:

if I do no water change for a year and therefore have a negligible KH when my tap is circa 6-10KH, then I do a 60% water change.

Not only adding a KH to a depleted KH setup. Massive rise within half an hour. Double that with I add cold water pulling the temp from 25 to 21.

Within half an hour I've caused a massive swing in KH, also a massive swing in temperature. Goes without saying the Ph will be massively different too.

Zero deaths, zero reaction from fish and shrimp alike. Plenty of spawning over the following week though

The problem with low KH and CO2 addition is measuring it. Therefore with this difficulty it is easier to gas the fish.

AC

 

[Katch]

so maybe the answer is to use two solenoids set to open and close together. that way if one fails you have a second making sure flow is stopped and started.

 

[PDSimon]

I'm confused, a solenoid staying open would not cause the fish any harm, as it just controls whether the co2 goes through not how much of it goes through....? I thought the biggest problem was the regulator being unreliable. If so, the solution would be to get a decent regulator. Horror stories happen with every aspect of fishkeeping and planted tanks so I think you're worrying too much

 

[SuperColey1]

The needle valve is the critical part. If this fails then the 'control over the CO2 is gone and loads goes into the tank. The regulator control should never be used as it isn't accurate enough.

Therefore we use the regulator to open/close and not control the rate. The needle valve then controls with a lot more precision the amount going into the tank. It is highly unlikely to fail although it easy to damage the needle by closing it all the way in.

Even if the regulator does try to 'dump' the needle valve will limit it.

Solenoid can be a major problem if you are away from home or just don't notice.

When we use a solenoid we are basically blasting the tank with CO2 in the photoperiod and then leaving the other 16+ hours to return to equilibrium and give the livestock a break. Blasting the tank outside of the photoperiod with no uptake means a most likely outcome of dead livestock.

Some do run 24/7 but are injecting at a much lower rate over the 24 hours. their setup is to try and reach a mx where the fish are still 'happy' at lights on. It will mean that the uptake reduces the CO2 quite a lot during the photoperiod but that doesn't really matter as long as for the first few 'peak' hours of the photoperiod there is sufficient CO2.

I have run both and didn't notice a particular benefit or advantage either way. The 24/7 does use more CO2 but not much as the injection rate is so much lower. However I prefer to use a solenoid as it means with the turbulence I use 24/7 that the CO2 is gone pretty quick after it switches off and therefore the fish have a 'CO2 free' period.

AC