Floating plants and water changes

Someone asked about this a couple of weeks ago (sorry I don't remember who). They were especially concerned about plants that "don't like getting their leave wet" and the effects of dunking them.

My procedure is to pump out around 100 liters of water from this tank. I don't move the plants out of the way and then suspend 25 litre jerry cans of water above the tank and open the tap so lots of plants get dunked.



IMHO the plants are doing just fine with this treatment.

They get rained on in the wild and you did say they are doing fine.

The main issue with some floating plants getting wet, is fungus and mould that grows on the leaves if they are permanently damp. This is commonly seen in Water Lettuce, Water Hyacinth and Water Lilies when they are kept under coverglass. There is insufficient air flow around the leaves and they start to rot. If you keep these plants in aquariums, they will do much better without a coverglass or hood on the tank. Most other floating plants (Duckweed, Azolla, Water Sprite) are usually fine with covers and high humidity.

Colin_T said:

The main issue with some floating plants getting wet, is fungus and mould that grows on the leaves if they are permanently damp. This is commonly seen in Water Lettuce, Water Hyacinth and Water Lilies when they are kept under coverglass. There is insufficient air flow around the leaves and they start to rot. If you keep these plants in aquariums, they will do much better without a coverglass or hood on the tank. Most other floating plants (Duckweed, Azolla, Water Sprite) are usually fine with covers and high humidity.

Click to expand...

The part about no cover never occurred to me. That's a great solution when you have the entire surface covered by floating plants anyway. If your room humidity is too low you could mist them occasionally. Plus it gives some of the larger floaters like Water Lettuce room to grow upward. Jumping fish aren't a concern with the plant cover shown in the picture.

Without a glass cover I know I could watch the water level drop in winter.
As far as floating plants and humidity, I've yet to ever see a problem....and it goes without saying that fast growing floating plants are the very best to aid in water purification.

Permanent conditions and temporary (during water changes) conditions are very different as Colin and Back mentioned.

As for a tank cover, there are good reasons to have a tank covered. First, dust from the air will settle on the water surface faster and in much greater density without a cover, and this is certainly not at all good for the fish/biological system. Second, some fish need warm air above the water (anabantoids especially, but also any fish that regularly gulps at the surface like cories, otos, hatchetfish, pencilfish, etc) and the cover ensures this. Third, many fish will jump especially during darkness if they get startled, and they do, frequently. Fourth, the amount of warm water evaporating from an open aquarium is more than you might realize (as Abbeysdad pointed out) and this will get into the structure of the house much like moisture in bathrooms, and that is something you do not want in rooms that are not ventilated to deal with this.

My floating plants, which include Salvinia, duckweed, Water Sprite, Water Lettuce, Frogbit, and Pennywort, do not seem bothered by my covered tanks.

Mine are covered - but I do leave the feeding hatches open in hot humid / weather.
The main reason for the post was that some people appeared to be genuinely concerned that their plants would die if they got dunked during a water change. As several have pointed out there is a big difference between getting wet and staying wet.

And just for fun...
Here it is 24 hours later

The ceiling is way more interesting than the floor, even the corys go foraging up there. I did a really brutal pruning on the substrate a few weeks ago. The vals were all set for world domination so I ripped most of them out. I wasn't sure the Amazon Swords would recover but they are making a brave effort.