Filtration and oxygen

[Michael]

Had a power cut recently - hence all gurgling etc stopped in my son's tank. It was the middle of the night so I just put a blanket over it and thought, I'll sought it out in the morning. Come morning, temp was fine. Fish panting a bit though (my son's cichlids don't hang around the top when short of oxygen, they pant - ie heavy breathing). Surprising because there are only a half dozen 3-4 inch cichlids, a 5 inch loach and a handful of fry (36" x 15" tank - forgive the imperials please). Anyway, power came back on but the air pump, which had siphoned water into itself through the air line, was not happy . Now with the power filter going and the heater on, the fish really started panting. The pump fortunately responded to some drying out and was now raring to go :lol: so I hooked up to the airstones in the under-gravel uptakes. Fish still panting after some time. I had recently read about an interesting issue with filtration: the bugs in the filter that turn ammonia to nitrate use oxygen, whereas plants that also use ammonia release oxygen. I thought I should apply this bit of info. I stopped the power filter, took the airstones out of the undergravel filter uptakes and just let the bubbles rip. Fixed the problem, but took about half an hour (conclusive evidence? or not?). After that the old system with filtration was OK. It would be interesting to know how the oxygen demand in various filters compares with that of the fish. I think in this case it could have been greater. I remember reading somewhere that the worms and inverts in a field of pasture have a greater bodymass than the weight of stock the field can support. I wonder if it could be a bit like that with bugs and fish? Incidentally the article on filtration suggested plants as an alternative to filtration. How about circulating the water through a plant tank? Algal filter?

Michael.

[ajbroome]

Michael said...

> .... the air pump, which had siphoned water into itself through the

> air line, was not happy.

You can buy little 'non-return' valves to stop this or else just mount the

pump higher than the water level of the tank...

Not that anyone ever does... ;-)

> How about circulating the water through a plant tank? Algal filter?

People have done that sort of thing and it does seem to work to

some degree at least. For best results I think you'd want high light

levels on the plant/algae tank and fast growing species which you'd

need to *remove* from the filter and chuck out (or feed to the fish)

so that the dead plant material doesn't just decompose and return

all the nutrients to the water.

The trouble is, do you eckon you could have a big tank full of plants

but with no fish... it'd be *too* tempting... ;-)

Oh, and if the power goes off on something like that for an extended

period you can be in even more trouble...

Andrew.

[Warren]

If the power is off for more than 1 hour, most filters have a certain amount of dead bacteria in them. This produces ammonia. If the filter is restarted as soon the power comes back on, tha ammonia will wash back into the tank and the fish will suffocate. Ammonia impeads gill function.

If the power has been off for over 1 hour, it is best to flush the filter. If it is a canister or trickle or fluidised bed filter (the types most prone to bacterial death) the flush method is easy. Take the return hose from the filter outlet and flush 4-5 times the filter volume of water down the drain. This will remove more than 99% of the ammonia build-up. The filter can now be reconnected to the tank and the tank topped up.

If it is not a trickle filter, just gently wash the filter media in a bucket with some aquarium water in it. Empty the bucket and do a repeat rinse.

Disclaimer:

This method works for me, but is not guaranteed to stop fish duying after a power outage. If you don't want to be effected by power outages, buy a UPS.

[Ira]

I've had my filter left unplugged for a day and a half(Stupid of me, oops) and then plugged it back in. About an hour afterwards I tested the ammonia and there was none. This is on a tank with only a relatively light bio load though, about 50 tetras in 120ish liters.

I'd be really interested to see what the ammonia reading would be of the water coming directly out of the filter after being shut down for a few hours. I'd tend to think it would be very small, there isn't that much of a mass of bacteria in the filter.

Not arguing, Warren, just commenting.

[Warren]

Did you check the amount of ammonia in the filter? Checking the tank after an hour may not have shown anything if the ammonia had all been converted. What was the ammonia level 2-3 minutes after restarting the filter...

However, you're probably right about a low level of ammonia. Keep in mind however, - it only takes 1ppm to wipe out your tank. Ammonia is also more toxic as pH goes up (look out africans).

Probably depends on the type of filter media too. The more afficient it is, the bigger the problem.

Before I had a UPS that holds up all my tanks for a minimum of 3 days, I got away with just starting up the filter a few times too. I am only suggesting a method that is a safety measure. Do you really want to gamble a few minutes of work on all your fish??????......????

Please see my disclaimer from previous post.

[Ira]

There wouldn't be enough bacteria in the tank to convert more than a tiny amount of ammonia in one hour. If there was that much there would have to be a much higher constant production of ammonia to support them, otherwise the bacteria would starve to death until the numbers dropped back to just enough to match the production of ammonia. If the ammonia was about 1 PPM in the canister filter that would be diluted to probably less than .1 PPM even in a small tank. Anyone want to volunteer to shut off their filter to see? Next time I have a power outage or forget to reconnect the filter I'll try to remember to test it.

I guess .1 PPM might be enough to bother something like discus...But...I hate discus.

[Warren]

Not a problem in a Discus tank. pH is less than 7 (6.5-6.7) so there should be very little free ammonia, - mostly ammonium which is much less toxic.

Discus are a lot tougher than you think however. Of all the fish I've ever kept, I've found Oscars, Discus, Tiger Fish and Uara's the easiest to keep long term.

[Michael]

Quite an interesting discussion on all this. Seems like our cichlids might have been suffering from ammonia poisoning rather than oxygen deficiency. But another plus for the plants versus bugs: plants don't die and produce ammonia when the power goes off, or the filter stops for some reason.

As for Andrew's comment on the fish in the plant tank, well. . . I had thought, maybe just a couple. . . Perhaps the system would be prone to a little human error.

Michael.

[john1]

Hi michael

Imperials are quite ok. Actually I prefer them. It is easier to say 3' than 91.76mm. You did not tell us how much gap there is between the top and the glasscover. Surface area is very important. More than a lousy airstone. But if you are really concerned about a power failure invest in a pseudo uninterruptable power supply. By that I mean a cheap 80W converter, a battery, motorbike or sealed lead acid battery. A few electric components, cheap, and someone who can hook it up for you. You connect the filter(s), airpump etc. but not the heater, and bobs your uncle. The minute the power fails the battery takes over and runs everything, except the heater. The heater is not that important in a reasonable sized tank. In the tropics the water temperature can go down quite a bit. Think about it. For a few bucks outlay you can safely go away for a few days even with no power in the house.

John