Do surface plants increase water evaporation??

[Emily in Everett]

I have a 90-gallon tank with 30 gallon sump. I usually have to top off the sump once every 5-7 days to keep up with the evaporation. But over the last month I'm now having to top it off every 2-3 days - like with a 5 gallon bucket! Like I come back from a 2-day weekend and the filter sponges are exposed to the air!

The only differences I can see are the colder drier weather (though the humidity in our house hasn't changed much according to our weather meter); and the sudden explosion of Amazon frogbit (I introduced a few leaves a few months ago; took a while to get going; but now it covers 2/3 of the surface and would cover 100% if I didn't do a weekly culling). 

I'm curious if a solid cover of surface plants would change the rate of evaporation in a tank. Any ideas? 

Edited January 3, 2022 by Emily in Everett

[Chris]

If anything, I'd guess that plant cover at the surface of the water would decrease evaporation, not increase.

In a recent livestream, Cory even said that a dense cover of floating plants has been known to decrease levels of Oxygen in aquariums - meaning that less of the surface of the water is able to exchange oxygen with atmosphere. In my (non-scientist) brain, that makes me think that it'd also decrease the total amount of surface area that could be used for evaporation.

[Seattle_Aquarist]

On 1/3/2022 at 12:25 PM, Emily in Everett said:

I have a 90-gallon tank with 30 gallon sump. I usually have to top off the sump once every 5-7 days to keep up with the evaporation. But over the last month I'm now having to top it off every 2-3 days - like with a 5 gallon bucket! Like I come back from a 2-day weekend and the filter sponges are exposed to the air!

The only differences I can see are the colder drier weather (though the humidity in our house hasn't changed much according to our weather meter); and the sudden explosion of Amazon frogbit (I introduced a few leaves a few months ago; took a while to get going; but now it covers 2/3 of the surface and would cover 100% if I didn't do a weekly culling). 

I'm curious if a solid cover of surface plants would change the rate of evaporation in a tank. Any ideas?

Hi @Emily in Everett, @Chris is correct.  The transpiration process (plants loss of water through their leaves) is much slower than the evaporation process.

Edited January 4, 2022 by Seattle_Aquarist

[Odd Duck]

In my tanks that grow floaters like crazy, the evaporation is noticeably less.  You need to look for a small leak.

[BuzzDaddy21]

Well as I read this I wonder if your tanks have lids??? (What am I missing about this.)😕

I`m not too smart about aquariums but I don`t have evaporation with lids. 

 

[gardenman]

The humidity in your house hasn't changed much as your fish tank is humidifying it for you by evaporating quicker in the winter months. It's basically serving as a humidifier for you.

[Aaron S]

It's the colder weather. Plants would decrease evap. 

Warmer air can hold more water... This, "relative humidity."

Lets say the humidity outside is 60%. 

That air, and all the water it's holding comes inside and gets warmed up. That relative humidity drops. Meaning, it can take on more water easily. 

The humidity in your home has remained stable by taking more water out of your fish tank. 

Maybe you've noticed, though house plants grow less in winter, they need more frequent watering for the same reason as your tank levels are going down faster.