A Simple Guide To Aquarium Auto Top-Offs


Automatic top-off systems are the best way to create a consistent water level in your aquarium. A consistent water level will keep your water parameters stable, providing a stable environment for your animals. An auto top-off will also save you time and make it easy to maintain your water level during a vacation. Added benefits include better protein skimmer performance and supplement dosing.

Here is a detailed list of the benefits of an auto top-off:
Increased Stability – Maintaining water levels is critical to maintaining your water parameters. When your water evaporates it causes many water parameters to change. Simply put, when the water evaporates there is less water and the same amount of everything else. This means that when water evaporates your calcium, ammonia, nitrate, phosphate, and salinity concentrations all increase. Adding an auto top-off can reduce these changes and provide a more stable environment for your animals.

Less Maintenance – Using an auto top-off is easier than manually replenishing water on a daily basis. When an average sized reservoir is used most people will go a week before needing to refill the reservoir. A larger reservoir will allow you to go even longer between refills. This is great for aquarists who travel frequently.

Consistent Water Level – Some pieces of aquarium equipment, such as protein skimmers and surface skimmers, do not function well when the aquarium water level changes. Adding an auto top-off can ensure this equipment will function optimally.

Simple Supplementation – Auto top-offs can be used to automatically dose certain supplements. Simply add the additive to the top-off water and then small amounts of the additive will be added throughout the day. Some additives that work well with auto top-offs include Seachem Flourish Excel, Seachem Kalkwasser, and Brightwell Aquatics PhosPhatE.

Videos Demonstrating How an Auto Top-off Works:
Which Auto Top-Off Should You Purchase?
The number one concern with auto top-offs is the failure to turn off. If this happens the salinity in your tank could drop significantly, causing harm to the animals in your tank. Water could spill onto the floors ruining your floors and possibly become an electrical hazard. Any additive added to the auto top-off would be overdosed. Additionally, you’ll want a unit that is low profile and low maintenance. With this in mind here are five of our favorites at different price points.

IceCap ATO – The IceCap ATO EZ System is a newer auto top-off that uses two optical sensors to measure the water level in the aquarium. These have no moving parts and are more reliable than the float valves in the JBJ. The unit also includes a pump and is only slightly more expensive than the JBJ.

Neptune Systems ATK V2 Automatic Top-Off Kit
The Neptune Systems ATK V2 Automatic Top-Off Kit integrates with the Neptune Apex Aquarium Controller or can be used by itself. It uses dual optical sensors and a backup float plus other features such as pump timeout to make sure the unit is super reliable. The ATK is a more expensive option, but one that is definitely worth it if you would like more features or already have an Apex Controller.

JBJ Nano ATO - The JBJ Nano ATO Advanced Auto-Top-Off System Is a successor to one of the most popular ATOs of all time. This simple and highly affordable unit comes in at half the price of some of the other ATOs and it has a very low profile sensor ideal for placing in small compartments of all in one nano aquariums such as the Coralife BioCube.

SpectraPure Liquid Level Controller – The SpectraPure Liquid level Controller has the largest but most reliable sensors. It can connect directly to a reverse osmosis unit so that you never have to add top-off water ever again. You will not need to place a water reservoir near your tank. The only downside to this unit is the sensors use suction cups that eventually fail.