My fish died overnight, and I don’t know why!
It’s absolutely heart-breaking to wake up in the morning and find your fish floating in the pond – especially when you don’t know why it happened. If they don’t have any visible wounds on them, and it’s mid-Summer in Phoenix, the cause is probably suffocation.
Several factors can contribute to this issue:
If any (or all) of these factors combine with the already low oxygen levels in warm water, the pond fish can suffocate. Here in Phoenix, during the summer, our nighttime lows can remain above 90 degrees! This sets up a very oxygen poor environment in our water to start with. Warmer water naturally holds much less oxygen than colder water.
What goes in must come out
An over-abundance of plant life provides plenty of oxygen in the daytime, but exhales carbon dioxide at night (photosynthesis). That’s right: too many plants allowed to grow out of control actually rob your pond of oxygen at night. Now, that’s not so bad in the wintertime, when cold water is oxygen-rich and the fish’s metabolism has slowed to a dormant rate, so they’re not in need of as much. But in the summer, the fish are more active, their metabolism is at full-throttle, and they need all the oxygen they can get.
Plants grow like wildfire in Phoenix from Spring through Fall, taking up the nutrients from the fish waste and adding shade and oxygen to the water all day long. Then nighttime comes along, and the plants reverse this process, stealing oxygen from the pond and releasing carbon dioxide, just like a human inhaling and exhaling. If you have a lot of fish (measured in inches) competing for that oxygen, someone’s going to lose -- and the plants can hold their breath longer than the fish.
Sun exposure, aeration, depth, plant varieties, etc. play a role in healthy pond-keeping practices. The following preventative measures are rules of thumb, and you need to remember that each pond is an individual and unique unto itself.
Pond Size & Fish Load
The first rule of ponding is to not over-fish your pond. Yep, there are a lot of really cool fish out there, and people are tempted to collect them all. If you want to do that, build a bigger pond with appropriate filtration for that goal. Otherwise, choose wisely.
Experts agree that you should keep your fish collecting to between ½” and 1” of fish per ten gallons of water. And if you have other aquatic life in the pond, such as a turtle, you need to take that into account, as well.
A well-maintained ecosystem pond really should only need a complete drain & clean every 3-5 years here in Phoenix. Preventative measures can extend that timeframe, or even eliminate it. That estimation changes depending on how many fish you have, other aquatic life in the pond, and how much food and waste accumulate.
The toxicity of the mulm building up on the floor of a pond depends on many factors: the types and size of your fish, the circulation system on the pond, the filtration system on the pond, etc. Preventative measures like netting the floor or adding sludge digesters to the pond regularly could actually keep you from ever having to worry about this issue.
If your pond wasn’t originally planned for abundant fish-keeping goals, you should err on the side of caution when adding fish and stick to the ½” of fish per 10 gallons of water recommendation.
If you’re just starting to think about a pond, you need to make sure you (or the professional you’re hiring) are clear on your goals of desired fish-keeping so that the design of the filtration system is appropriate.
Keep plants under control
This is a big part of maintaining an ecosystem pond. In the wintertime, it’s no big deal because the water is cold and both the fish and plants are fairly dormant. Plus, a bit of extra dormant plant material in the pond makes for great cover for over-wintering amphibious life.
But once Spring hits, those plants start growing like crazy! Just trimming off the dead leaves isn’t enough. You need to make sure you’re keeping the roots under control – which also has the added bonus of preventing water displacement leaks. A good rule of thumb is to keep your plants from covering over 50% of the pond’s surface area. If you have stellar aeration, you can have more; less aeration, less coverage. Sun exposure and depth play a role, as well.
Pond Maintenance Programs
Ponds need regular maintenance. Most well-built ecosystem ponds with appropriate filtration for their size need as little as 10 minutes a week, and provide hours of enjoyment. But it has to be done.
If you are unable, unwilling, or just plain too busy to do the maintenance, but still want a gorgeous living water feature, The Pond Gnome has maintenance programs for folks who want to do a little, a little more, or not a bloody thing!
How can we help?