I recently added an AZOO fan to the back of my JBJ 28g HQI and my evaporation rate went through the roof. Not that it bothers me, I'm just curious if it's good for the tank, with the theory of oxygen exchange, as long as the ATO keeps the salinity level consistent. Any ideas?
Evaporation, Good or Bad?
- Thread starter frgarcia
- Start date
Generally a plus but it really depends on what's in the air around the tank and CO2 levels in the tank.
For exampe, a tank with a lot of photosynthetic activity with pH in say the 8.3 area and low gas exchange with the air , would experience a drop in pH if room air CO2 is high when gas exchange is increased.
For exampe, a tank with a lot of photosynthetic activity with pH in say the 8.3 area and low gas exchange with the air , would experience a drop in pH if room air CO2 is high when gas exchange is increased.
blanden.adam
Team RC
Neither? It's a process that does things. It cools the water, which may or may not be beneficial at any particular time (e.g. I cool my tank via evaporative cooling with a fan and temperature feedback, so when my tank is too hot, it's beneficial, when my tank is at temperature, it's not beneficial). It increases salinity, which also may or may not be beneficial. If I have a fish in quarantine at a lower salinity (like 1.018 sg for example) and I'm trying to bring it up to reef salinity slowly (1.025-1.026 sg), then evaporation is beneficial, if I'm trying to maintain a small tank at an appropriate salinity without an ATO, it's not beneficial. See where I'm going?
Increased oxygen exchange? Not really buying it. Sure blowing a fan over the surface of the water might have the effect of increasing fresh air circulation over the top of the water and therefore increasing oxygen concentration, but that doesn't have anything to do with evaporation, just the fan -- evaporation is a bystander in that instance. Even then, it depends on whether or not you get adequate air exchange without the fan. I guess what I'm trying to say is it is a process that happens, we can take advantage of it in several instances, and must mitigate its effects in others, but calling evaporation objectively "good" or "bad" isn't really possible.
Increased oxygen exchange? Not really buying it. Sure blowing a fan over the surface of the water might have the effect of increasing fresh air circulation over the top of the water and therefore increasing oxygen concentration, but that doesn't have anything to do with evaporation, just the fan -- evaporation is a bystander in that instance. Even then, it depends on whether or not you get adequate air exchange without the fan. I guess what I'm trying to say is it is a process that happens, we can take advantage of it in several instances, and must mitigate its effects in others, but calling evaporation objectively "good" or "bad" isn't really possible.
leveldrummer
New member
yep, evaporation = cooling, thats pretty much all. if your tank needs to be cooler, then good, otherwise your just topping off more water.
smatter
Active member
The wiener dog made me smile ^^^. My latest pico is completely covered with a tight-fitting piece of glass. The tank can go a week without any top off water. Gas exchange isn't an issue because circulation is provided by a powerful air pump. The less evaporation the better if heat isn't an issue.
Depending on the situation and conditions evaporation may be good or bad or not important one way or the other.
Surface agitation and evaporation are hard to separate in the op' s post but they are obviously different things beyond contextual semantics.
Nonetheless, I took the package presented and my comments were related for the most part to enhanced gas exchange(not necessarily oxygen) resulting from enhanced surface agitation causing the evaporation in this case. The agitation creates a larger surface area to interact with surrounding air than calm water does. Whether or not more gas exchange is helpful depends on the surrounding air and the tank and the biological activity in the tank ;usually enhanced gas exchange is a plus for many reef tanks in terms of CO2 off gassing and /or O2 replenishment during nightime hypoxic conditions but that is not not always the case..
As for evaporation alone it will cool the water, so in that sense it will allow the water to hold more oxygen and other elements like carbonate and calcium.. It could also give you more room for top off which could be important for some dosing limewater as an example.
There are downsides,in sg fluctuations,increased salt creep,variability in element concentrations,most of which can be managed with an ato set up.
Surface agitation and evaporation are hard to separate in the op' s post but they are obviously different things beyond contextual semantics.
Nonetheless, I took the package presented and my comments were related for the most part to enhanced gas exchange(not necessarily oxygen) resulting from enhanced surface agitation causing the evaporation in this case. The agitation creates a larger surface area to interact with surrounding air than calm water does. Whether or not more gas exchange is helpful depends on the surrounding air and the tank and the biological activity in the tank ;usually enhanced gas exchange is a plus for many reef tanks in terms of CO2 off gassing and /or O2 replenishment during nightime hypoxic conditions but that is not not always the case..
As for evaporation alone it will cool the water, so in that sense it will allow the water to hold more oxygen and other elements like carbonate and calcium.. It could also give you more room for top off which could be important for some dosing limewater as an example.
There are downsides,in sg fluctuations,increased salt creep,variability in element concentrations,most of which can be managed with an ato set up.
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The point is the increased surface area from surface agitation enhances gas exchange including evaporation./aka vaporization as the liquid turns to a gaseous phase and enters the surrounding air when that air has less than 100% humidity. Even if the water in the tank were heated to evaporate it the outcome would be vaporization . "Gas exchange "which can be significantly increased as water surface area volume increases and vaporization occur together.
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blanden.adam
Team RC
I think all Tom is trying to say is that many of the processes that increase aeration also increase evaporation. They are certainly different things and don't really effect each other, but often occur at the same time. For example, increasing surface agitation increases the surface area for gas exchange and breaks up the organic film that forms at the top of the water, both of which increase aeration and also happen to increase evaporation.
Duvallj
New member
Air flow above the tank could help gas exchange, but not due to the evaporation.
In some situations where the air-flow above the tank was almost non-existent more airflow might help.
Example being a 5 sided canopy or those glass tops.
In most peoples tanks however canopies are ussually vented for heat make it the chances adding air flow to increase gas exchange moot.
As for evaporation being good or bad... With an ato it makes a cheaper alternative to cooling a tank than a chiller. I say can be used for good if you can control the fan.
In some situations where the air-flow above the tank was almost non-existent more airflow might help.
Example being a 5 sided canopy or those glass tops.
In most peoples tanks however canopies are ussually vented for heat make it the chances adding air flow to increase gas exchange moot.
As for evaporation being good or bad... With an ato it makes a cheaper alternative to cooling a tank than a chiller. I say can be used for good if you can control the fan.
TimeConsumer
Active member
Nobody should be using tap water regardless of evaporation rates.
I's not the air flow per say that increases gas exchange ; it's the increase in the water surface area( ripples ,etc) . Even a tank lidded with glass as several of mine are will get enhanced gas exchange from exposing a larger water surface area to the air that ciruclates if there is an opening for fresh air across the back as is usually the case.
Thanks Adam for making it clearer.
I agree aeration and evaporation are different. It's an important distinction.
They do both occur when air blows across the water surface.
For calrification:
The moving air increases water surface volume which enhances gas exchange/aeration.
Evaporation itself plays little role( the cooling effect a bit of one perhaps) in gas exchange/aeration other than as water in it's gaseous form ,i.e, water vapor.
The increased water surface area meeting the surrounding air also enhances evaporation .
The air movement by wind over the water also decreases air pressure on the water which also makes it easier for water vapor and to escape.
The process to separate water molecules from the water uses heat and cools the water.
The humidity of the surrounding air is obviously influences and is influenced by evaporation .
I agree aeration and evaporation are different. It's an important distinction.
They do both occur when air blows across the water surface.
For calrification:
The moving air increases water surface volume which enhances gas exchange/aeration.
Evaporation itself plays little role( the cooling effect a bit of one perhaps) in gas exchange/aeration other than as water in it's gaseous form ,i.e, water vapor.
The increased water surface area meeting the surrounding air also enhances evaporation .
The air movement by wind over the water also decreases air pressure on the water which also makes it easier for water vapor and to escape.
The process to separate water molecules from the water uses heat and cools the water.
The humidity of the surrounding air is obviously influences and is influenced by evaporation .
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