Saltwater Aquarium Beginner's Guide | Episode 5: Clownfish, Water Parameters & Kalk
This is without a doubt, the most painful part of setting up a new aquarium...waiting for the tank to finish cycling. Fast forward two weeks from episode 4 of this series, and the tank is finally ready. Matthew has been water testing daily, and we have watched both ammonia and nitrite peak and return to zero, indicating the cycle is complete.
That progression tells us beneficial bacteria are established and converting waste properly. With the cycle complete, the system is now stable enough to support livestock.
To help speed things along, several proven bacteria sources were added early in the process. AlgaeBarn NitroCycle was used to seed the tank, along with pre-seeded biological media from an established, healthy reef tank. If you do not have access to an existing system, options like Aqua Natural Live Filter Media can offer a similar jump start. A bottle of Fritz Aquatics TurboStart was also added to further strengthen the bacterial population and shorten the time it takes to reach a stable cycle.
What Should You Test for in a Reef Tank?
99.9% of the time, once the cycle is established, testing for ammonia and nitrite becomes unnecessary. Unless something very bad is happening, these values should remain undetectable on our hobby-grade test kits.
After the cycle, hobbyists generally test for six main water parameters:
- Temperature: Temperature is one of the easiest to measure accurately. There are several easy to use digital options out there and even some that double as heater controllers.
- Salinity: This is another easy one that is crucial to success. After all, this is what makes a saltwater aquarium a saltwater aquarium! A handheld refractometer is the most popular testing device, but there are some great digital testers that are quickly gaining popularity like the Hanna Salinity Tester.
- Alkalinity: Sometimes just referred to as "Alk," alkalinity is the water's buffering capacity against pH changes, but maybe more importantly, it's half of the "stuff" needed for corals to create their hard skeletal structure.
- Calcium: Calcium is the other half of the "stuff" that corals need to create their hard skeletal structure. It's often thought of as the most important by new hobbyists, when in reality, calcium changes relatively slowly in the average reef aquarium when compared to alkalinity.
- Nitrate & Phosphate: Let's lump these two together for now as they are the two water parameters commonly called "nutrients" in the aquarium hobby. High levels of phosphate are commonly thought to lead to nuisance algae growth, but overall sentiment in the hobby has been evolving over the last few years to focus less on phosphate levels and more on the microbiome and herbivore population in the tank when trying to solve algae problems.
Matthew's Target Water Parameters
- Alkalinity: 9 dKH, but anything between 8-10 dKH
- Calcium: 400-450 ppm
- Nitrate: Above 0 ppm, but below 20 ppm
- Phosphate: Above 0 ppm, but below 0.1 ppm
Of course, there is a lot more to pay attention to in a reef tank, so we'll post a parameter guide with more details. Click on the image for a downloadable .PDF to print for a handy reference.
How Often Should You Test the Water in a Saltwater Aquarium?
Matthew plans to test nitrate, phosphate, and alkalinity weekly long term, but more frequently in the first few months. Calcium will be tested for occasionally, but typically doesn't drop as quickly as alkalinity, which is why many reefers choose to use alkalinity as a canary parameter. Not to mention, Matthew will be using kalkwasser, which increases both calcium and alkalinity together.
Every situation is unique, but use this as a rule of thumb for testing frequency:
- Temperature: Monitor daily
- Salinity: Weekly
- Alkalinity: Weekly
- Calcium: Every 2 weeks, or if you see a drop in alkalinity
- Magnesium: Every 2-4 weeks
- Phosphate: Weekly
- Nitrate: Weekly
- Trace Elements: It's a good idea to send in an ICP test at least once per year, but don't worry about this until the tank has coral and is more established.
Kalkwasser: What, How, and Why?
Kalkwasser (aka Kalk) is just a fancy German word for lime water. More technically, it's Calcium Hydroxide, a powder that is added to RO/DI water, then slowly dosed to a reef tank over a long period of time either via a dosing pump or mixed with water in an auto top off reservoir.
What Does Kalkwasser Do?
Kalk is used to maintain calcium and alkalinity levels and has the added benefit of increasing the pH of the aquarium water.
How Does it Work?
Don't worry, I'll keep this easy to understand. No chemistry formulas here!
As we now know, kalkwasser is Calcium Hydroxide. The calcium part is simple with calcium being available for the corals to use right away.
The alkalinity part involves one extra step. The hydroxide part reacts with carbon dioxide that is dissolved in the water to form carbonate and bicarbonate (what we measure as alkalinity). A result of this reaction is a lower level of dissolved CO2 in the water. Because carbon dioxide lowers pH, this removal causes the pH to rise! To avoid dangerous pH spikes, it's very important to add kalkwasser to the aquarium slowly over time.
What Are the Pros and Cons of Dosing Kalkwasser?
| Pros of Dosing Kalkwasser | Cons of Dosing Kalkwasser |
|---|---|
| Calcium and Alkalinity in One
Kalkwasser adds calcium and alkalinity in a balanced ratio, simplifying dosing and reducing the need for multiple additives. |
Limited Dosing Volume
You can only dose kalkwasser at the rate your tank evaporates, which limits how much calcium and alkalinity can be added each day. |
| Boosts pH
Reacts with carbon dioxide to add calcium carbonate and bicarbonate to the water, helping increase pH |
Not Good for Corrections
Kalkwasser works best as a maintenance solution and is not effective for quickly raising low calcium or alkalinity. |
| Easy to Automate
It can be dosed with a pump or mixed into auto top off water, making it easy to run consistently. |
Evaporation Dependent
Seasonal humidity changes affect evaporation, which means kalkwasser dosing often needs seasonal adjustments. |
| Affordable
Kalkwasser powder is inexpensive compared to most multi part dosing systems. |
Maximum Saturation Limit
There is a hard limit to how much kalkwasser can dissolve in water, which caps its total dosing capacity. |
| ATO Failure Risk
If an auto top off system sticks on, it can add too much kalkwasser at once and cause a dangerous pH spike. |
|
| Only Addresses Calcium & Alkalinity
Kalkwasser does not add any magnesium or trace elements to the system, which may need to be dosed separately down the road. |
How Do I Dose Kalkwasser?
Ok, so you want to dose kalkwasser. HOW do you do it? Let's walk through this together, step by step.
Step 1: Test for Calcium and Alkalinity
This one is pretty self-explanatory. We need a baseline for these two parameters as they're the two that kalkwasser will affect.
Step 2: If Calcium and/or Alkalinity Are Too Low
Because kalkwasser isn't good for making larger adjustments, you'll need to adjust calcium or alkalinity independently with either a calcium chloride or sodium bicarbonate solution.
I recommend the Kalkwasser Starter Package because it comes with not only kalkwasser, but also chemicals to adjust your calcium, alkalinity, and even magnesium.
Step 3: Determine the Method You'll Use to Dose the Tank
For this example, we are going to be adding kalkwasser to the auto top off reservoir. Other methods include using a dosing pump and/or kalkwasser reactor, but we won't go into those options for this beginner guide. You can learn more about those options in this BRS Pharma Kalkwasser Guide.
This step assumes you have an auto top off (ATO) system set up on your aquarium. If you don't, we highly recommend it! ATOs are not only massively convenient, but also provide better salinity level stability for your tank inhabitants.
Step 4: Mix the Kalkwasser Powder Into the ATO Reservoir
Depending on your system's demand for calcium & alkalinity, you can add up to 1.5 teaspoons (NOT tablespoons) of BRS Pharma Kalkwasser to the ATO reservoir.
As a rule of thumb:
- Low Demand - 0.5 tsp per gallon of freshwater
- Medium Demand - 1 tsp per gallon of freshwater
- High Demand - 1.5 tsp per gallon of freshwater
Stir vigorously while you add the powder and keep stirring until it's dissolved. It's always best to start on the low end and add more to the next refill, if needed.
There are a few things you'll probably notice next:
- A film will develop on the top of the water. It's a feature, not a bug! The film helps protect the solution from the surrounding air that contains CO2. Once mixed, don't mess with it until the reservoir needs to be refilled.
- You may notice some "stuff" at the bottom of the reservoir that doesn't dissolve no matter how hard you try. This is referred to as kalk slurry. Some experienced aquarists have been experimenting with dosing kalk slurry, but if you're new to the saltwater aquarium hobby, it's best to avoid dosing this directly to your tank.
Tips:
- Always add the kalk powder to the RO/DI water and never the other way around.
- Position your ATO pump about an inch off the bottom of the reservoir so it can't suck up the kalk slurry.
- Clean out the ATO reservoir after every few refills to remove the leftover kalk slurry.
Step 5: Consider ATO Tubing Placement
Make sure the ATO is adding water to a high-flow area or move it to a higher flow area if necessary.
Step 6: Monitor Water Parameters
Turn the ATO system back on and monitor the tank's pH, calcium, and alkalinity. If this is your first time adding kalk to your system, test daily for the first week to get a better understanding of how it's affecting the water parameters.
Getting the Tank Ready for Fish!
The wait is over. All of the planning, preparation, and time spent maintaining water has led to this moment! It's time to add the first fish to the system. But, wait! You can't just throw them in there and hope for the best.
Here's the Tentative Tank Stocking Plan:
- Stage 1 (you are here): Pair of clownfish
- Stage 2: Clean up crew, macroalgae, gorgonians, and a few more fish
- Stage 3: The rest of the livestock! (TBD)
Clownfish are arguably the most iconic saltwater aquarium fish. Even most toddlers know what a clownfish is thanks to that one movie. Just don't call them "Nemos" and we can still be friends.
The best news is that nearly all clownfish in the hobby are captive-bred, meaning they haven't been taken from the ocean and are a super sustainable option.
We partner with Oceans, Reefs & Aquariums (better known as ORA) to offer around 300 varieties of captively bred fish, corals, and invertebrates. And boy does ORA have clownfish options!
Acclimating Your New Fish
Acclimating fish simply means getting them adjusted to the water in the aquarium you'll be adding them to. There are two main methods for acclimation, each one better for a specific scenario.
Temperature Acclimation (Recommended for fish shipped to you)
- Turn off aquarium lights to reduce stress on the animal(s). Also turn off your ATO, if you have one.
- Float the sealed bag in the aquarium for about 20 minutes to equalize the water temperature.
- Cut the bag open and use a net to gently transfer the fish to the aquarium. Discard the water in the bag; do not dump it into your aquarium.
Parameter Acclimation (Recommended for visibly stressed fish or fish you buy locally)
- Turn off aquarium lights to reduce stress on the animal(s). Also turn off your ATO, if you have one.
- Float the sealed bag in the aquarium for about 20 minutes to equalize the water temperature.
- Open the bag and transfer the fish and water into a clean container.
- Acclimate by adding 1/4 cup of aquarium water to the container every 5 minutes for about 40 minutes.
- Use a net to gently transfer the fish to the aquarium. Discard the water in the container; do not dump it into your aquarium.
- If needed, add more saltwater to the aquarium to replace the saltwater you removed in step 4.
For future reference, bookmark this handy guide on How To Acclimate Live Fish & Corals Into A Saltwater Aquarium.
Observe Your New Fish, Wait 24 Hours, and Feed
That's it! Keep an eye on your new friends and add a little bit of food to make sure they're eating the next day.
Clownfish will eat just about any food they can fit in their mouths, but we like to feed a mix of frozen and pellet foods.
Feeding Tips:
- Clownfish always look hungry, so add a small amount of food at a time and only feed what they'll eat in a couple of minutes.
- Smaller, more frequent feedings are always better than a single larger feeding.
- Pellets are very nutrient dense so take care to ensure you aren't overfeeding.
- Add Hikari Seaweed Extreme Pellets into your rotation as clownfish are omnivores.
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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