Plant (Vegetable) Filters

[bekko]

Quote: So why are they turning yellow in your pond water?

There can be a lot of curious interactions. Too much nutrient can burn the plants. Ponds are notoriously rich in nitrogen and phosphate, but there is almost no potassium (the 'K' in N-P-K). When growing plants bare-root the roots can develop a coating of algae which steals all the nutrient before the vascular plant can get it.

Because you cannot measure ammonia or nitrate with a test kit does not mean that it is not being produced. It means it is being utilized as fast as it is being produced.

The important thing to remember is that plants do not "remove" nutrients from the system. They only tie up nutrients for a while and when a leaf dies all its captured nutrient is released back into the water. Nutrients are not actually removed from the system until the plants are thinned out and put on the compost heap. Do the math..... Compare the nitrogen content of wet-weight plant biomass which you remove from the bog to the nitrogen input via fish feed. You will find that a bog is a lot of work for not much benefit in terms of genuine nitrogen removal.

This is not to say that a bog filter isn't fun and (hopefully) beautiful. Also, there are likely benefits which we are overlooking. The uptake of excess trace minerals and heavy metals which enter the pond via feed could be one of them. Providing a buffer to stabilize the concentration of dissolved nutrients when the feed input is inconsistent could be another.

-s tevehopk

[dOHd]

You are correct in the interactions. And too many time ponders only focus on the three negatives that we dont want, instead of also focusing on what we need, chemistry values which are either low or missing completely.

When you start talking trace minerals, there are many that are needed for proper metabolism by the fish, and also by the plants. Over time, these are depleted and need to be restored. That is great if your source water does the replentishment, or if you even change enough to matter.

And with water differences from one place to the next, it is difficult to recomend water changes for some people.

I can do and have done a flow through system. So if the plants have to have the ammonia, nitrite, or nitrate in measured amounts, why do they grow so well in a flow through system with no detectable amounts?

So for a person to mislead others into believing that their pond water is healthy because there are no traces of ammonia, nitrites or nitrates, and as a consiquence the plants are turning yellow, is only looking at the pond as a single dinamic, not as a complete system.

d

[MikeM]

dOHd: I think you have me confused with someone else's post? I do not have plants in the pond. None to yellow. (I do have a separate waterlily pond where fertilizer can be used when desired.) I did make the point early in this thread that a truly effective plant filter would not be growing beautiful plants. This is because the mass of plants would be sufficient to exceed nitrogen production of the fish pond. Only plants with low nitrogen needs would be able to take the competition, and these would not reach their potential. Taro is a plant adapted to nutrient deficient soils. Very efficient at capturing nitrogen where other plants struggle. But, as big as Taro can grow, it has extremely high water ratio. There is not much there compared to the volume you perceive. When dried, a 7' Taro's weight is a matter of ounces. So, a lot of mass created by the water-retentive cell structure on very little nutrient. I think your large weekly water changes are the key to your water quality... and I applaud you for doing them. A koikeeper with good source water has a wonderful resource and should take advantage of it.

[dOHd]

Mike

Sorry for the confusion. But the question still remains for those that use that indicator as the basis for their assumptions.

The leaves on the trees are also full of water. But dried, they also weigh nothing. And I have other plants as well as the taro that also do well.

Actually, I have a shop where I sell plants. One of the things I have noticed is that even with no fish in the display tank, and no fert. tabs, they do just nicely with regular water changes to the tanks.

My point was this. Water gets used up. Fish, bacteria, other life forms all use up micro nutrients in the water that are necesary for life. Unless that water is refreshed, those nutrients stay missing. Plants are just the first to visually display your problem. Plants turning yellow is not an indication that you have a healthy pond.

People that push plant filters as the solution are just like the pond builders that tell you that you need 20 tons of gravel in your pond for the pond’s health. Plants can be a part of the solution, but they can not be the total solution.

I don’t rely on veggie filters. But I do have plants in the ponds, even the pond with the big girls. And every one of them grows well. Not because I need them, but because they add a dimension to the pond I enjoy. And none of the plants are potted, but instead bare root. That way there are no dead spots, no addition to the bioload etc. I can not keep lilies in the pond with the big girls, as they would destroy them in under an hour.

The most serious issue I see is when the power goes off, and the fish are deprived of the O2 in the water. There are times plants make this situation worse, taking the hour or so you could have to respond to a power failure, and making it only minutes before fish deaths start.

Then there is the subject of pH swings, but that is another subject as well.

d