Dear Pug Fish:
What a terrible shame! All my condolences on the loss of your ponies. Summertime heat waves and power outages happen all too often and when they happen to coincide it’s always bad news for seahorses. The loss of power shuts off your filters and airstones and protein skimmers no longer generate a bubble stream, and the resulting lack of circulation and surface agitation rapidly causes a drop in dissolved oxygen levels and a rise in carbon dioxide levels due to the respiration of the seahorses and their tankmates. It sounds like you were as well prepared as possible to deal with such a crisis, but there is only so much you can do when circumstances beyond your control conspire against you.
At the same time, the loss of air conditioning and elevated water temperatures that result increase the metabolism of your seahorses, and therefore their consumption of oxygen, at the very time that the rise in temperature is further reducing the amount of dissolved oxygen the water can hold. This creates a doubly dangerous situation for seahorses and results in rapid, labored breathing, hypoxia, and eventually death by asphyxia or suffocation.
Like other seahorses, Mustangs and Sunbursts will begin to experience heat stress and associated health problems whenever the water temperature rises to 80°F or above for any length of time, and that’s almost impossible to avoid when a prolonged power outage takes place during a heat wave with temperatures reaching 100°F or more for days on end. It sounds like you made a valiant effort to cool the tank using the available ice, Pug Fish, but I know that the supply of ice runs out very quickly during summertime power failures as well, so unfortunately there was not much more that you can do under the circumstances.
But the primary problem for the aquarist when there is a power failure is a massive die off or tank crash due to a drop in the dissolved oxygen levels and a corresponding rise in carbon dioxide. How quickly this becomes problematic depends on the size of the aquarium and the number of fish and invertebrates it houses. The smaller the tank and the greater the number of specimens it contains, the quicker they will deplete the available oxygen and begin to die off, so with small heavily stocked tanks it’s very important to restore power as soon as possible. A larger tank with just a few specimens will have a larger margin of error before the dissolved oxygen is exhausted. But whenever there is a power outage, you should strive to provide the tank with oxygen one way or another as quickly as possible to save your biofilter and prevent losses due to asphyxiation.
Seahorses are more vulnerable to low O2/high CO2 levels than most fishes because of their primitive gills. Unlike most teleost (bony) fishes, which have their gills arranged in sheaves like the pages of a book, seahorses have rudimentary gill arches with small powder-puff type gill filaments. Seahorses are said to have "tufted" gills because they appear to be hemispherical clumps of tissue on stems. Their unique, lobed gill filaments (lophobranchs) are arranged in grape-like clusters and have fewer lamellae than other teleost fishes. Because of the difference in the structure and efficiency of their gills, seahorses are thus especially vulnerable to low oxygen levels and asphyxia.
In a pinch, you can make an effort to manually aerate and oxygenate the tank by scooping pitchers of water and pouring them back into the aquarium from a height of 6 inches or more, but you are really fighting a losing battle that way and it will positively wear you out if the power is out for any length of time.
Aside from such stopgap measures, better solutions are available if, like Pug Fish, you prepare in advance for the next brownout or prolonged power outage, as discussed below.
To begin with the obvious, if you live in an area that’s prone to power outages, investing in a backup generator is something you may want to consider. But there are also a number of other less costly measures that can help the aquarist and his fishes make it through a power outage without suffering devastating losses. For example, here are some excellent tips from Dan at the org regarding how hobbyists can cope with power outages:
"Some possible options besides a generator are:
Battery operated pumps. Some of the bait pumps that use 2 D cells can
run for up to 4 to 5 days and can drive 2 to 3 airstones. Besides
aerating the tank, it also helps to aerate the biological filter if
Computer Uninterrupted Power Supply (UPS). They can be real handy. If placed inline with your equipment it can seemlessly keep stuff running for short durations or
drive air pumps for quite a while.
Deep cycle marine batteries with an inverter. During the hurricanes,
we pulled the batteries and the inverter off the boat and ran quite a
bit of equipment off these for 24 hours.
For short term unexpected outages, battery operated pumps and/or
computer UPS are probably the most economical answer. For long term
outages, such as a hurricane, a generator will pay for itself the first
time it is used.
Another consideration for long term outages, is to have plenty of water
available. Often long term outages lead to water availability issues."
The decrease in dissolved oxygen levels is not the only threat to your aquarium when there is a power failure. You must also be aware of filters and equipment that doesn’t automatically restart once the power comes back on, and if you have a sump or refugium connected to the main tank, water siphoning our the main tank can also be a huge headache, as Al explained in this previous post:
I have so many power outtages here and often of such long duration that I
feel like I`m living in a third world country so I`m way too familiar with the quandary, "WHERE
DID ALL THIS WATER C0ME FR0M?" in the aftermath of a power failure.
If you use a tank/refugium combination that are on different levels, water
siphoning down out of your main tank through air hoses or the water pump return
hose will be a problem. They do sell air check valves that prevent this from
happening with air hoses, or you can make a loop in the air line that remains
positioned AB0VE the main tank`s water line which will prevent a gravity fed
back-flow through the airline.
Water siphoning back into the refugium from the main tank through the water
pump or other inlet/outlets can be avoided by:
a) placing the return hose outlet to the main tank AB0VE the water line.
This will cause a break in the water column should the pump fail and it also
creates greater surface turbulence during normal operation
b) place the pump return hose near the surface of your main tank and make
sure your refugium/wet-dry filter can contain the excess water that could siphon
off the main tank before the level drops sufficiently to break the water
c) if your tank is bored out and fitted with bulkheads anywhere lower than
the top few inches of the tank, get some extension hose or PVC piping to make a
loop for the inlet that is above the water line in the main tank and a loop
that is just below the water line for the overflow/outlet. These loops will
limit the water lost out of the main tank in the event of a power failure.
Another annoying problem is caused by hang on filters and other magnetic
impeller driven devices that won`t restart on their own <as well as many canopy
lights> after a power failure. Some brands of hang ons need to be *primed*
before they will start moving water again, others need their impellers coaxed a
little. Turn your tank power off for about 20 minutes and test where you`re
likely to have problems.
In short, folks, if you have a power failure and you’re lucky enough to have a generator, get it fired up as soon as possible to be on the safe side, and then doublecheck all your aquarium equipment to make sure that everything has started up again and is operational.
If you’re not so fortunate as to have a backup generator, head out to your local fish stores or sporting goods stores and get some battery operated air pumps and load up on plenty of Duracells ASAP. Have someone manually aerate your tank(s) in the meantime to maintain the dissolved oxygen levels until you can get back and get the battery-powered air pumps operating.
Pete Giwojna, Ocean Rider Tech Support