# A lesson relearned



## BryceM (Nov 6, 2005)

I came home a couple of days ago to see all the fish gasping at the surface of my 180g tank. Several of them had a "dead on the bottom" appearance. Some of the amano shrimp were lying on their sides. A look at the pH controller showed the pH to be 5.50. NOT GOOD! The light on the controller showed that the power to the solenoid was off.

Well, the solenoid might have been "off" but it was stuck in the "on" position. This is with a Milwaukee combination regulator/solenoid/bubble counter/needle valve unit. I quickly did a partial WC, got an airstone going, and within a couple of hours everything looked good again. Out of 100 fish I lost maybe 2 or 3 little ones and the shrimp seem fine. WHEW!!!!

Lessons learned?

1) Adjust the bubble rate to keep the controller from cycling on & off frequently.
2) Build redundancy into the system. I think I'll add an alarm to the low side of the pH controller.
3) Buy good quality stuff to start with, especially on a 180g show tank.


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## bugs (Jul 19, 2006)

I spotted that my solenoid had stuck open after the power was off at the end of last week. I noticed as I was locking up for the night - in the usually silent room I could hear the CO2 running in the darkened tank. If I'd been on holiday... or even just away for the night.

Fish health v. plants... Fish win every time. Tired of all the CO2 expense and hassle, the above being the final straw, I stripped the whole lot out, downgraded from 3 to 2 light tubes, and stopped EI dosing. Currently all seems OK - maybe better than before, although it's early days.


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## Zapins (Jul 28, 2004)

Hmm interesting, and something I've worried about since learning of the Milwaukee solenoid regulator flaws. How do you plant to build an alarm into the pH controller?


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## gotcheaprice (Sep 4, 2007)

Ahh... That sucks. Luckily not too much died, though I guess unlucky that some did.
Are you gonna get any new stuff?


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## Rex Grigg (Jan 22, 2004)

One solution is to go with a high quality needle valve and 24 CO2 injection. If low O2 at night is a problem then an air pump on a timer will solve that.


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## BryceM (Nov 6, 2005)

Building in an alarm into the pH controller is easy. The Pinpoint controller closes one circuit when when the pH is too high and another when the pH is too low. Currently I have the CO2 solenoid hooked up to the "pH is too high" side. If I simply attached a 110V buzzer or flashing light to the "pH is too low side" it would let me know.

Speaking of new stuff, I'm placing an order with Rex this week, thank you very much. With a good needle valve I plan on setting things so that CO2 flow is just high enough that even if the new solenoid sticks open it won't hurt anything.


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## kwc1974 (Jan 4, 2006)

I use redundent slenoid valves for my CO2 systems.
Cheap insurance, learned my lesson the hard way too.


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## gotcheaprice (Sep 4, 2007)

Haha, so, are you getting a non solenoid too?


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## kwc1974 (Jan 4, 2006)

Yeah it did sound that way, HA
Sometime what you mean to say and what is said

To clairify, I use two valves togeather, one as a failsafe.


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## BryceM (Nov 6, 2005)

How do you know if one of the two has failed?


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## kwc1974 (Jan 4, 2006)

I guess this is where the engineering designer comes out in me (always plan a back-up)

every now and then I will check to make sure both are working individually. If both are working fine I connect them back up. If one should ever fail I will replace it (with out the need to stop CO2 injection).

To some this sounds like overkill or overcoming inadequate equipment. I use this method with even the top of the line equipment.


It may be overkill, I know, but I have lost hundreds of dollors in fish/shrimp before. Don't really want to go through that again.


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## BryceM (Nov 6, 2005)

I've thought of running two separate pH controllers, each with its own pH probe and solenoid valve. That way both would need to be in agreement about a high pH state before the CO2 could flow. The engineer in me likes this idea, but the financial planner in me can't quite see it through to completion. CO2 is one of the most toxic substances in existence, depending on dose. That 20 lb cansiter is just waiting for the chance to nuke everything in the tank. We treat it without much respect much of the time. For a 20g tank with a few fish, a disaster is limitted in scope. In a 180g tank with hundreds of fish and shrimp, its a much larger loss to stomach. The solenoid only needs to stick once to cause issues. Random testing might not reveal a problem.


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## kwc1974 (Jan 4, 2006)

You are absolutly right, but I think that the compromise that I have given my self by running two soleniod valves is both econimicly sound and better than waiting on the one valve to stick. It is not the best solution, I agree, I like you can not bring my self to spending the money to do it the way I would with an unlimited buget. So like I said I alowed my self the compromise, something is better than nothing.

Good idea (costly) with the dual pH controllers, I have always been leary of getting a pH controller (how can you trust the one to work without constantly checking after it) but if both match then you have a failsafe. The real technical side of me would want to put the two outputs on a controller to give them a system of "if both read X ph, then do this".......excuse me while I tell myself to shut up for thinking too much.


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## Rex Grigg (Jan 22, 2004)

CO2 one of the most toxic substances in existence? And adding the weasel words "depending on dose" makes it even worse.

Hmm... you may be an engineer but you must have flunked both Chemistry and Organic Chemistry. CO2 is pretty innocuous.

Check out http://chemistry.about.com/cs/5/f/blpoison.htm

I love this statment



> Water will kill you if you drink too much of it. Oxygen is a deadly poison, yet we need it to live.


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## BryceM (Nov 6, 2005)

Ah Rex..........

You enjoy looking around for a chance to pounce on this sort of thing I suppose. I don't really want to get into a flame war with you.... especially not here.... especially since I'm buying some parts from you, but honestly.....

To be fair, CO2 is not in the same league as arsenic, cyanide, or inhaled plutonium. Dead is dead though, and plenty of planted tank nerds have sent plenty of fish to fishy heaven with their CO2 management schemes. People are quite creative in finding ways to kill their fish, but of all the things a planted aquarist may inadvertently overdose into the aquarium, CO2 is probably in first or second place when it comes to lethality. Plenty of people have been killed by it too. That makes it plenty toxic in my book.

CO2 is transported in the body by three mechanisms. The first is as a simple solution in blood plasma. The second is by the formation of carbamino compounds with various proteins. The majority of CO2 is carried by the bicarbonate buffering system. A rise in the blood CO2 level causes shifts in plasma pH by depleting available bicarbonate buffers. 

CO2 levels also affect hemoglobin's binding affinity for oxygen. The presence of CO2 shifts the hemoglobin oxygen dissociation curve. This effectively diminishes the ability of blood to carry O2. Within reasonable limits, the biochemistry of vertebrates is well equipped to accomodate temporary shifts in CO2 levels. A large, rapid increase in CO2 (like with an end-of-tank dump or stuck-open solenoid) creates a situation where the body can no longer compensate. Blood oxygen levels fall, neurological hypoxia results and DEATH follows.

Finally, I think a personal attack on my supposed grades is rude and uncalled-for in my own thread on a public forum. Correcting objective factual errors or politely expressing a difference of opinion on subjective matters is entirely different, and is appropriate. I love the chance to discuss controversial or emerging issues as friends. Name calling and childish insults make a weak argument. I'll be happy to furnish copies of my college and med school transcripts to anyone who is truly interested, but I ask the same in return........

I await your response, and then I think it's probably best to close this thread, since it appears to have already outlived its useful purpose.


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## Zapins (Jul 28, 2004)

guaiac_boy, I like your idea about the dual pH controller setup, however, it might be nearly impossible to get both pH controllers to agree on a reading before opening the CO2 solenoid. Might have to design a chip to give it some range of tolerance. Say +/- 0.2 pH or so. Could get complicated...


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## Rex Grigg (Jan 22, 2004)

You made a statement without qualifications. If you had stated it was one of the most toxic substances we could put into an aquarium I might have agreed with you. But you made a blanket statement that is sure to come back and scare the crap out of some newbie reading this thread.

And actually the most toxic thing you can put into your aquarium that we deal with on an regular basis?

Untreated water.

Do a 50% water change with untreated water (from a municipal water system) and you are going to kill fish.

Some people do die from CO2. But only in weird stupid cases. Many more people die from CO every year. CO2 is a very common compressed gas. If it were dangerous you would not find it in every location that dispenses soda and/or beer. I can dump an entire 20 lb cylinder in my living room and it will not harm me. The same can not be said for other common compressed gases. I would guess that more people in the US are killed from Mono Dihydrogen Oxide poisoning every year than CO2 poisoning. Crackhead mothers giving the baby bottles of water instead of formula happens quite often. Even adults have been killed by overdosing on water. But it's a real under reported story when it happens.

When you get right down to it O2 is actually much more of a hazard (as a compressed gas) than CO2.

Of course a CO2 system failure that results in large amounts of CO2 entering the aquarium is going to kill fish. But that's a long way from



> CO2 is one of the most toxic substances in existence, depending on dose.


I like to see things through the eyes of someone reading this thread with no knowledge of CO2. And your statement is not factually correct.


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## BryceM (Nov 6, 2005)

Zapins,

If the controllers don't read exactly the same value it's not really a problem. Suppose each is set to open the solenoid at pH >6.50 and close when the pH is <6.30. The solenoids are connected in series, so if both are closed there is no gas flow. If one is open and one is closed there is no gas flow. If both are open there is gas flow. Assume this starting condition with a small error between the two readings:

If controller #1 shows a pH of 6.45 and controller #2 shows a pH of 6.49, both will be closed.
If controller #1 shows a pH of 6.49 and controller #2 shows a pH of 6.53, #1 will be closed.
If controller #1 shows a pH of 6.53 and controller #2 shows a pH of 6.57, both will be open.

Once they are both open pH falls as CO2 is added. Controller #1 isn't quite calibrated correctly, so it reads a bit low. When it hits pH 6.30, it will close solenoid #1. Solenoid #2 won't close, but gas can't flow so pH starts to rise. If solenoid #1 happens to stick open, controller #2 will quickly reach pH 6.30 and it will close solenoid #2, allowing pH to rise.

You'd still need to check each solenoid for proper function once in a while but it would really require a double failure to kill the aquarium. The problem of a solenoid that only sticks once in a while is still an issue though, since it's hard to realize that it has failed. It might also be a huge PITA to get both controllers to stay calibrated enough to function correctly. Who knows. Its more of a thought experiment than a practical solution IMO.

Having a second pH monitor with appropriate alarms would also provide a fail-safe mechanism, but only if you are around to monitor it and correct the problem. Some fancy setups can send a text message via cell phone or pager to alert the user, but this sort of things gets expensive pretty quick.


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## kwc1974 (Jan 4, 2006)

Exactly how it should work, in theory.

But lets look at this from another perspective. What if instead of controlling th CO2 form over dosing, we find a way to fix it if it does. When the pH goes too low, indicating a spike in CO2, you automate a air pump to help diffuse the excess CO2.

Just another idea I had, thought I would share see if some one else would take it to the next step if it was worth doing.


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## Zapins (Jul 28, 2004)

Yea actually that might be more simple kwc1974. 

Come to think of it 2 regulators hooked up to one another would need a good metal joint between them, or the pressure from the one nearest the CO2 tank would pop the tube off the second one.


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## BryceM (Nov 6, 2005)

No, not 2 regulators. Take an average CO2 setup (a single regulator, solenoid, needle valve, & bubble counter) and simply add one more solenoid in-line, next to the first one.


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