Cycling, Lighting, and Auto Top Off | Saltwater Aquarium Beginner's Guide: Episode 4
Cycling, lighting, and auto top off. Wow, do we have a lot of great info to cover in Episode 4 of this series!
Cycling a Saltwater Aquarium
What the heck does "cycling" an aquarium even mean? If you've been researching how to set up an aquarium for any length of time, you've probably seen the term cycle or nitrogen cycle more than a few times.
Simply put, cycling an aquarium means to prepare its biological filtration’s ability to process ammonia into less harmful things like nitrate and nitrogen gas.
To put it less simply...
When we add food to our tanks, that food is packed with nutrients. The leftover food and any fish waste eventually break down and become ammonia. From there, beneficial bacteria (Nitrosomonas) consume the ammonia and convert it to nitrite, which is less toxic. Then different bacteria (Nitrospira, Nitrobacter, and Nitrospina) take nitrite and convert it to nitrate, which is even less toxic than nitrite.
Once we end up with nitrate, it's typically removed in one of three ways.
- Removed manually via water changes (most common)
- Converted to nitrogen gas by anaerobic bacteria (this isn't as common in our aquariums as they typically don't have many areas where anaerobic bacteria can thrive)
- Consumed by live plants or macroalgae.
Water Testing During the Cycle
Once the cycle begins, regular water testing is the only way to know what’s actually happening in the tank.
During the initial cycle, you’ll only need to test for three parameters:
- Ammonia
- Nitrite
- Nitrate
If you're new to the aquarium hobby, try testing every 2 to 3 days and write down your results so you can track trends over time. I recommend this practice to any new aquarist because it really does help you better understand the nitrogen cycle.
We’re watching for a very specific pattern: ammonia rises, then falls as nitrite rises, and finally nitrite falls as nitrate rises. That progression tells us beneficial bacteria are establishing themselves and converting waste properly. Once nitrite peaks and falls near zero along with ammonia, the cycle is considered complete.
Nitrate is the final byproduct of this process and isn’t a big concern during cycling, so don’t panic if those levels start to climb. We’ll handle nitrate later through water changes and other nutrient-management methods.
Saltwater Aquarium Lighting
Picking the right lighting for a saltwater setup is all about your end goal. If you're happy keeping a fish-only system, commonly called FOWLR (fish only with live rock), just about any lighting that looks good will do. If corals are more your game, then you'll need to put a bit more thought into the lighting you place over the tank.
The Right Light Intensity
Light intensity is just as important as light quality. Corals rely on light to fuel photosynthesis, but each type of coral has a preferred range of PAR (Photosynthetically Active Radiation). Too little light and they’ll struggle to survive. Too much light and they may bleach or become stressed. The goal is to match the intensity of your lighting to the needs of the corals you plan to keep.
During the early stages of a new aquarium, it’s best to run lights at low intensity to help keep nuisance algae under control. As the tank matures and corals are added, intensity can be gradually increased over time. Using a PAR meter will help dial in the perfect levels throughout your aquascape, but we'll talk more about that down the road.
Low vs Medium vs High-Light Corals
- Low-Light Corals: Most soft corals like leathers and mushrooms as well as some LPS like Chalice, Micromussa, and Blastomussa.
- Medium-Light Corals: This is most LPS corals and some lower light SPS. Examples include Torches, Hammers, Frogspawn, Montipora, Birdsnest, and Digitata.
- High-Light Corals: Acropora are going to be the biggest group of corals in this category. While many corals can adapt to high light, it's best done very slowly over time.
The Right Spectrum
The perfect light intensity means nothing if it isn't the right kind of light. In short, if you buy a light designed for a reef tank and that meets the intensity needs of the corals you plan to keep, you should be safe.
If you want to get a little nerdy with me for a moment, we can dive a layer deeper into what makes a light "good for corals." Corals depend on their symbiotic relationship with photosynthetic algae known as zooxanthellae to survive and grow. These microscopic algae reside within the coral's tissues, converting sunlight into energy. We aim to mimic the natural light conditions found in the coral's ocean habitat, particularly emphasizing the blue spectrum that supports optimal photosynthesis.
Generally speaking, the 400 to 480 nm range is what we pay closest attention to. This range covers light from the very edge of UV and everything in the blue spectrum range.
AquaIllumination Blade LED Light Fixture
For this build, we’ll be using a pair of AquaIllumination Blade Coral Grow LED Strips. These smart LEDs are extremely low profile and offer some of the best value in terms of cost compared to light intensity output. The Blade series is designed specifically for reef tanks and provides the spectrum corals need to photosynthesize and thrive, especially in the blue wavelengths we rely on for growth and coloration.
Another big advantage of Blade fixtures is their simplicity. The tank rests make installation straightforward without the need for a separate mounting arm or hanging kit. The lights can be easily controlled through the Mobius app, where we can set schedules, adjust spectrum, and fine-tune intensity as corals are added over time.
As the tank matures and we begin introducing photosynthetic animals like corals and anemones, we’ll revisit our lighting setup to ensure we’re delivering the right PAR levels across the aquascape. For now, the goal is to get the lights mounted safely, set them on an appropriate schedule, and enjoy seeing the tank come to life.
Auto Top Off Systems
An Auto Top Off (ATO) system is typically one of the first pieces of automation equipment a saltwater aquarist will buy. In a saltwater tank, the saltwater stays behind as the water evaporates. This means that as water evaporates, the salinity level of the aquarium gradually increases. To combat this, we top the tank off with fresh RO/DI water. But in some systems, this causes large salinity swings, which are unhealthy for the tank inhabitants. I think I can speak for the rest of the BRS team on this one, that an ATO system is a long-term 100% absolute must-have addition to a saltwater aquarium. It's better for the animals and allows us to step away from the tank for a few days without salinity problems.
How does an auto top off system work?
Every ATO system has two main parts. A sensor to detect the water level and a pump to add freshwater when the water level drops below the sensor. For this build, we're using the Tunze Osmolator 3 Nano. The only other thing we'll need is a container to store our freshwater. We'll be using an acrylic ATO reservoir from Trigger Systems here, but something as simple as a 5-gallon bucket will get the job done too.
Three important notes when installing an ATO system:
- Install the ATO sensor in the return pump chamber. This is the only area where the water level will change with evaporation, so installing the sensor elsewhere will render the ATO system useless.
- The output of the ATO tubing should NOT be submerged. Doing so will cause a backsiphon that will drain water from your aquarium into your reservoir.
- The ATO reservoir should be installed below your aquarium. If the water line in your reservoir is above the output of your ATO tubing, a siphon will form and water will continue to run from the reservoir into the aquarium until the water level in the reservoir drops and the siphon breaks.
Coming Up Next
Episode 5: Clownfish, Water Parameters & Kalk
Adam has been reef keeping since 2010 and got his start on the Bulk Reef Supply Customer Service team. He believes the best tanks are built around what you enjoy, not what’s trending. Adam is especially interested in simplifying the hobby, exploring the latest gear, and helping others focus on long-term success over chasing perfection.
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