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I read all the time about the importance of maintaining adequate oxygen in the water. Is there a way to measure oxygen in the water?

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Leo,

    While it is true that only a portion of the oxygenation from regular atmospheric bubbling of the water using air pumps and air stones comes from the actual bubble to water contact as the bubbles rise, that doesn't negate the fact that those bubbles rising in the water column is actually pretty effective at mixing the water in the tank to bring bottom water to the surface to get aerated and those bubbles actually disturb the surface of the water (not just by bursting at the surface) but simply by roiling the surface (causing little waves.)

Anything that disturbs the surface, mixes the water, splashes or sprays will help with aeration.  A water pump that is on a separate circuit that simply moves, sprays or splashes the water can serve as an aeration backup, it doesn't HAVE to be an air pump, that is just often an easy way to do it.

One benefit with air pumping is you can actually use a single air pump to provide aeration on two separate systems without mixing the water in any way while it would require two separate water pumps to do the job while maintaining system isolation.

While the larger pumps will work well is many situations I think I would go with at least one pump for every tank. If something happens to a large pump feeding several tanks then you have issues in several tanks instead of just one. A better option might be 2 smaller pumps per tank as a back up if one fails.

Yes, I tend to do this by using an air pump for each tank or system and then the system also has a water pump that provides circulation and aeration.  In a perfect world I would have the air pumps on a battery backup fail over switch in case mains power fails.

Jeff Sullivan said:

While the larger pumps will work well is many situations I think I would go with at least one pump for every tank. If something happens to a large pump feeding several tanks then you have issues in several tanks instead of just one. A better option might be 2 smaller pumps per tank as a back up if one fails.

However, one might need to examine their situation carefully to decide if many separate pumps (and hence power points) is really a viable option.  If you do NOT have the means to get backup power wired in for all separate set ups and don't have two separate circuits for EACH tank (since a major common fail point that could affect both pumps, like the breaker or cgfi tripping on the circuit that both are plugged into kinda defeats the safety of having two separate pumps per tank.) Then one might want to look into a larger air pump that could be served by a single backup power source and just the air plumbing needs to be run out to each individual tank rather than having to run double/duplicate wiring out to each tank to have enough circuits.

I have so far not lost any fish due to a pump failure (well unless you count the time the grate failed and a fish got sucked into the pump) but I have lost an entire tank full of fish when the CGFI tripped on the circuit that both the water pump and air pump were on due to a storm.  We didn't realize anything was wrong till it was too late either since it wasn't like the power everywhere went out, only that one circuit.

Anyway, for many people it is not necessarily safe for them to be running their own power circuits around the place and they would have to hire an electrician to do it so I can understand a situation where one might be willing to use a larger size backup air system common to many tanks since it would likely not require running lots of extra circuits and wiring.  Especially since a separate fail over switch, battery, Relay, inverter, and pump for multiple systems could actually become more costly to buy, install and maintain long term than a single larger Backup system.

The choice on this might be tricky since systems often grow over time and you might not know where you need the power points run when you have the electrician on hand doing the work but of course the larger the air system the more power it uses and backup systems for large power consumption tend to get very costly in themselves and it is all balanced by what you have the budget for at the time.

How about 2 large pumps on separate circuits allowing 2 air lines to each tank for redundancy with 1 power back up. Just another option for the larger enthusiast. Most of us I feel are 1-4 tanks so elaborate back up systems would be overkill.

Well I think having two separate air pumps per system is way overkill.

Remember that you are also getting aeration from your water pumping and circulation system (unless your system is operating on airlift pumping.)

So I figure that one of my pumps for the system is the water pump and that is going to be a separate pump per system and I try to put them on a different circuit from the air pumping.

Then I want some form of separate aeration system.  This could be in the form of an air pump for each system or a larger air pump that covers all systems but this one I definitely want on a separate circuit than the water pumping and if at all possible I do like to have a power backup for the air pumping (I did at the old house, I just need to get more batteries and inverters and all that hooked up here.)

I don't see it as necessary to have two separate air pump systems for the fish tanks, at least in my systems since the air pumping is actually a redundancy in itself.  As long as the water pumping is circulating, spraying and splashing the water I'm not likely to kill fish just because the air pump quits.  (My fish varieties don't need extreme oxygen levels, if the water pumping alone isn't enough to keep your fish alive, then you might want the extra redundancy.)  If the air pump quits or the water pump quits during hot weather the fish still survive but will be off their feed until I get the problem sorted out but I don't expect a fish kill as long as one or the other is working and they are not getting fed while the system is limping along in such a fashion.

If you do go for the total double redundancy (like two water pumps plus two air pumps) make sure there is some sort of indicator that will let you or other tenders realize that the main is down and you need to fix something since it might not be easily noticed at a quick glance when going out to feed or walking past the tank if you see water flowing and air bubbling.  A system where the main has failed and you are only running on the backup without noticing and gets left that way is just as in danger of experiencing failure as a system with NO BACKUP.

Consider Cosmo's backup indicator system using colored lights, if all the colored lights are not on, then something might be wrong and need to get checked out.  Usually this is not for the operator but for the people you leave to tend things when you go away for a holiday.

I agree with TC. If you have all these separate air pumps and water pumps you have to ck every one every time. If you have one RELIABLE air pump you only need ck one FT to see that all is ok. And that applies to the water pump as well. That is why I have resorted to using the best quality for each. The commercial little air pump I posted as an example, previously, will out last the "consumer" aquarium pumps probably in the order of 50 to 1. My air pumps were OLD when I removed them from the metal pile at the dump on Cape Cod some years ago. I forgot I even had them BUT after dealing with the "vibrator" style consumer air pumps and becoming very disappointed with their poor performance the light went off and I rummaged thru my storage semi and I have not looked back. The consumer pumps are on the shelf for now.
The best BU in terms of failure is to buy the best and then get a BU and have it ready. I am willing to bet that my pumps were in operation for 20 yrs BEFORE I grabbed them (based upon what they came out of) and put one to use in our system and WITHOUT rebuilding them it has been running quietly for nearly 2 yrs now 24/7 aerating 5 full size IBC FTs.
I want to clarify one thing. These pumps are diaphragm style pumps BUT they are built like a tank with way oversize ball bearings, heavy duty diaphragms and robust crankshafts. On top of that they are what's called "positive displacement" like a car engine. That means they do not lose pressure easily and therefore will push air to the bottom of a 4' deep IBC in stride. Vibrator or the "solenoid" types (solenoid style are very loud by all reports) simply start to stall given any back pressure. That is why they don't work well on larger deeper systems. Then there are the turbine types that are very inefficient and expensive and again not good for pressure but produce large volumes of air. Basically a sophisticated form of fan if you will. Car motors have been positive displacement for over 100 years for good reasons. At 50.00 you cannot beat one of these little commercial pumps. New they sell in the 4-500.00 range because they are so well built in such a small package.
As to BU systems keep an eye out for commercial size UPS units on Ebay as well. I pu a 1400 watt ADC unit that will charge 2 large 12v or 4 golf cart bats and take care of everything in a power outage for many hours without a sound or any hands on at all. I spent 85.00 delivered for what had been a 2-3000.00 unit new. I got it originally for my printer that I make up to 16 foot panoramas on and a power outage would be very costly in the middle of one of those prints. Commercial surplus again is the way to get the best at a fraction of the price of the consumer models.

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