The Pond, Part 3

When we began to build a pond, we thought we had quite a bit of experience with ponds already. The main difference between our old pond back in South Carolina and our new one here in Costa Rica was principally size -- the new one is almost 50 times bigger than the old one. As much water evaporates daily from our new pond as the total volume of the old pond. We've discovered this was an oversimplification. We grew water lilies, but they were hardy water lilies, not tropical ones. We had koi, but they eventually were eaten by predators. So, we didn't know what would happen over the long haul. We had frogs, but they were different species than the ones here. When we put all of these differences into a dynamic, interacting system of plants and animals, we found we were constantly facing new situations and new challenges.

Water harvesting seems to be working well. It is too complex a system to explain it all here, but  in essence, our 1,100-gallon storage tank works as a reserve for the pond. In the dry season, we collect as much as we can in the tank, and then pump it into the pond as needed. This last dry season was actually pretty wet, and we only had to add city water to the pond about twice a month. In the rainy season we get too much rain -- the overflow could cause errosion problems downstream. So, as soon as the reserve tank fills up, we pump it into the pond. Thus, when the next rain comes, it doesn't overlow into the pond until the reserve tank is full again. This gives us a cushion.

We have four kinds of fish -- koi, goldfish, swordtails, and angelfish. Someone warned us that the angelfish were very territorial and would go after the other fish. This may be true for aquariums, but it has apparently not happened in the pond. The koi have grown by leaps and bounds. A couple of them are now about 10 inches long. They are very colorful and we love to watch them.

The swordtails give live birth, and have been prolific. We started with about a dozen, and now have somewhere between one hundred and two hundred. The koi lay eggs. We're guessing that many of the eggs get eaten by other fish. We now have at least eight baby koi, measuring from one to three inches long. We haven't seen any baby angelfish or goldfish yet.

Me, with the first water lily

Our original water lily began to pine away and eventually died. This was very upsetting to us. We'd never had a water lily die on us before. We're not sure what the problem was. About three weeks ago I had a chance to get another water lily. I was at a gathering of gardeners at the Biesanz Woodworks in the nearby city of Escazu and Barry Biesanz offered me one of his beautiful white lilies from his pond. He even had wading boots for me. They came all the way up to my armpits. I thought it was a bit of overkill, but it turned out I really needed them. It was difficult to see in the murky pond water and I ended up taking Barry's largest and most beautiful plant. It was unintentional. I promised myself I was really going to take care of this one.  I planted it the next morning in a pot that was almost twice as big as the one I'd used before, and I gave it some really good soil and organic fertilizer. I also put some extra heavy stones on top of the soil, to be sure the koi didn't bother the roots.

The amphibian population has changed. The frogs we had captured and brought to the pond stopped croaking months ago. We haven't seem them either, but our handyman said he saw one last week. One evening in early April we began hearing what sounded like a large bullfrog croaking. I suspected it might be a cane toad, so I looked up the call on the internet, and sure enough, that's what it was. We learned that cane toads are poisonous, and can be lethal to a dog if it should bite the toad. Fortunately, the toads seem to be staying near the pond, which is fenced off.  About ten days after we heard the first toad, he was joined by another one, and then another, and then another, until we had at least six toads. They've been serenading us every evening for two months now, and we just love it. Most of them have left in the last couple of days, so mating season seems to be coming to an end.

Cane toads mating

Okay, now we have the cane toads and the water lilies in the same pond. Sound like a good combination? Yes? Think again. The cane toads had lots of choices about where to lay their eggs, but they all chose the one big water lily. One morning we found the water lily floating on the surface. Gadzooks!!! What was going on? We pulled the water lily out of the water and discovered that the leaf stems were completely covered with about a three-inch layer of frog eggs. We figure that the jelly mass was so buoyant that it pulled the plant right out of its pot. We sprayed the eggs off with a high-powered hose, re-potted the lily, and are praying that it recovers from this catastrophe.

Many of the toad eggs had hatched before were able to remove them from the pond. Suddenly we had thousands of tadpoles. We don't know how many, maybe 10,000? We read in the literature that the tadpoles are, like their parents, toxic.So, we've been skimming them out of the pond. Each day the number decreases and we think we're down to only several hundred tadpoles at this point.

As reported in the last pond post, the water hyacinth are much smaller than they should be. I have created a separate section in the pond for them, so that the koi can't eat their roots. Unfortunately the koi have learned to jump the barrier, and seem to love to do it. So, my next project is to make it taller.

So, you can see the pond has been quite a challenge for us. Fish and amphibians are doing fine. Plants have been problematic. If the water lilies survive and prosper, we will be overjoyed.

Happy gardening!