- One of two things is eventually gonna happen
to you in this hobby either you'll get sick
and tired of manually filling your tank
with RODI water every single day
or you'll leave town for a few days.
Either one of these scenarios means it's time
for an ATO, auto top off units
or ATOs for short are some sort
of combination of float valves, sensors, and pumps.
Now their job is to sense low water
in your tank due to daily evaporation and flip
on a small pump to refill your tank with RODI water.
Just a quick reminder for all of you beginners out there
salt doesn't evaporate, only the water evaporates.
So when refilling your tank every day because of evaporation
be sure to only put in RODI water and not salt water.
There are various methods that ATOs use to
detect the water level in your tank.
The most simple is by using a float valve
gravity fed as the water level goes down, the valve opens
and gravity feeds RODI water into your tank.
As that water level goes up, it pushes the valve up
and it mechanically closes stopping the water flow.
The second way some ATOs detect the water level
is using a float switch or multiple float switches.
These mechanical floating devices trigger an on/off
for the small pump.
So whereas float valves are gravity fed
and electric free,
float switches require electricity in a pump.
Simple ATO units may only use one float switch
but fancier units out there may use more
than one for extra redundancy.
And lastly, you have optical sensors
with no moving mechanical parts.
These optical eyes can detect the water level.
While these may sound fancy and full proof,
optical sensors can also fail.
Okay, so technically you don't need an ATO
but I have yet to meet a hobbyist who has been in this hobby
for more than a year who has not eventually gotten one
because the only other option is to manually fill your tank
with RODI water every single day.
And trust me, I've done it.
It gets old really fast.
I have personally used seven different types
of ATOs and more than one has failed on me.
To maximize the lifespan of your ATO,
you're gonna wanna make sure
that you get the right one for your system.
The first consideration is where it's gonna go.
It will need to fit
in this same compartment as your return pump.
So do some measurements and make sure it's gonna fit.
Then you'll need to make sure the ATO can actually function
in that location.
For example, a Reef Breeders EXO auto top off unit
can only function through clear glass.
So if you intend to put this
on a black rear filtration chamber or in a colored sump
it's not going to work because the sensor actually
has to read the water level through the glass.
Lastly, consider the size of the pump.
ATO pumps are typically tiny
and many don't have much head pressure
meaning they can't pump water vertically sometimes
over three feet.
Also some have built-in fail safes, such as timers.
For example, if you put an undersized ATO unit
into an oversized tank, it may take a really long time
for that small pump to fill the water height
to the correct level.
And before that can happen, the fail safe timer may click
in shutting the pump off, meaning the RODI water
from the ATO unit will never be able to catch up
to the evaporation in your tank.
And lastly, you want to decide between float switches
and optical sensors or some sort of combination of the two.
Let me just be super honest with you.
I have had several optical sensor fail on me
but I have personally never had a float switch fail.
I'm not saying that float switches can't and won't fail.
I've just never had one fail.
So I don't want you to think
that a float switch is bad and an optical sensor is good.
They both have their pros and cons.
By far, the safest route possible will be to get an option
that has the most redundancy, usually some sort
of combination of optical sensors and float switches.
I just counted and I currently own 10 ATOs
but I have only had one of those since the beginning, 2013,
with the original pump that has never failed on me.
I am of course, talking about the TUNZE osmolator.
I'm not gonna lie to you.
It's pricey but I feel confident in saying this,
that's because it's the best out there.
With both a highly accurate optical sensor
and a backup float valve,
the smart controller will alert you
if there's a problem with an LED display
and an optional alarm.
It also comes with a built in fail safe,
which will detect when your pump is running dry
and shut it off.
I also have have the TUNZE Osmolator Nano here
which is designed for tanks
under 50 gallons with only a single float switch.
It does lack the redundancy of its bigger brother.
For those of you that either don't have the space
or aren't quite ready to shell out that much money,
I would recommend the Reef Breeders Prism.
I currently own four of them and I actually
like them better than they're more expensive counterpart,
The Reef Breeders Exo ATO.
The all in one sensor actually contains three
separate infrared sensors.
One to turn the pump on one, one to turn it off
and a third for extra redundancy
in case the pump fails to turn off.
I like these Prism ATOs, but certainly feel more
confident when I'm away with the built-in
redundancy and eight year reliability that I've had
with the TUNZE Osmolator.
To set up your auto top off unit correctly,
you'll need to select the correct compartment,
a correctly sized reservoir,
and the correct hose height.
Choosing the right compartment is easy
because there's only one correct choice.
You have to place it in the same compartment
that houses your return pump
because that is the only compartment
in your tank that will have a variable water height.
Choosing a correctly sized reservoir is more important
than you think if your reservoir is too small
you'll probably have to refill it every other day
which kind of defeats its purpose to begin with.
While on the other hand, if it's too large
and your ATO fails in the on position,
it could either overflow your entire tank
and flood your home
or it could dilute your salt water
to the point where you experience livestock death.
I think somewhere near to 10% is the magic number.
That means if you have a 50 gallon tank, go ahead
and install a five gallon reservoir, a 100 gallon tank
go ahead and install a 10 gallon reservoir.
At 10% of your overall water volume,
if your ATO fails in the on position
your tank will likely be able to hold the excess water.
Not only that, but if you run your tank
at 35 parts per thousand salinity,
a dilution of only 10% lowers that to 31.5,
which will probably be okay
for your livestock in the short term.
And lastly, the flexible tubing
for the ATO needs to be placed
above the water height in the reservoir.
If for some reason you that flexible tubing
below the water height in the reservoir
when that pump turns off, the siphon will continue
and gravity will keep filling your tank with RODI water
and ATO is made of mechanical and electrical parts.
So it has a lifespan.
If it fails and you're at home,
you can probably catch it before disaster strikes,
but what if you're away, there are three easy steps
you can take to minimize the risk.
Number one, reduce tank evaporation,
number two, build in redundancy and number three,
connect your RODI unit directly to your reservoir.
Randy and Ryan will teach you how to do all of those things.
And as always everyone, thanks for watching.
Happy reefing be well.
We'll see you next time.