Two Little Fishies Kalk Reactor Review: The Ultimate Calcium Booster for Reef Tanks
By Marina Holt
Marina Holt is a dedicated reef hobbyist with over a decade of experience maintaining mixed-species coral reefs. She specializes in stable water chemistry and has successfully transitioned numerous hobbyists from liquid additives to dry kalkwasser systems for superior long-term stability.
The Short Answer
If you are struggling to maintain stable alkalinity or calcium levels in your reef tank, the Two Little Fishies Kalk Reactor offers a reliable, automated solution to your water chemistry woes. This dry kalkwasser system dissolves calcium carbonate at a controlled rate, ensuring a steady stream of alkalinity and calcium without the mess of liquid additives or the complexity of manual dosing. It is particularly effective for mixed-species reefs that demand consistent pH and saturation state levels to thrive.
Who This Is For ✅
✅ Advanced reef keepers who need automated calcium dosing without manual intervention.
✅ Hobbyists with high-burnoff tanks containing large SPS or LPS colonies requiring constant saturation support.
✅ Aquarium owners who want to eliminate the hassle of mixing and storing liquid calcium supplements.
✅ Reef enthusiasts looking for a cost-effective alternative to expensive commercial kalkwasser reactors.
Who Should Skip the Two Little Fishies Kalk Reactor ❌
❌ Freshwater aquarium owners who do not need calcium supplementation for their livestock.
❌ Nano reef setups under 20 gallons where the dosing rate may overwhelm the system’s capacity.
❌ Hobbyists uncomfortable with electrical equipment running 24/7 near their water display.
❌ Beginners who prefer manual dosing schedules to better understand their water chemistry fluctuations.
Testing on My 150-Gallon Mixed Reef
I installed the Two Little Fishies Kalk Reactor in my 150-gallon mixed reef tank to address persistent drops in alkalinity during the summer months. The unit features a simple dry feed mechanism that I filled with calcium carbonate powder, which it dissolves using a heated element to create a slurry. Over the course of six weeks, my alkalinity stabilized at 8.8 dKH, and calcium levels remained consistently between 420 and 440 ppm. The pH stayed remarkably stable at 8.1 to 8.2, even when I increased lighting intensity for a coral fragging event.
The heating element works efficiently to keep the slurry from clogging, which is a common issue with cold kalkwasser systems. I monitored the feed rate daily and adjusted the settings to match my tank’s consumption. The unit operated silently, blending seamlessly into my tank setup without disrupting the visual aesthetic or creating noise that might disturb sensitive livestock. My nitrate levels dropped slightly as well, likely due to the improved overall water stability and reduced stress on the biological filter.
Quick Specs Breakdown
| Feature | Specification |
|---|---|
| Dosing Method | Automated dry feed with heated dissolution |
| Calcium Source | Calcium Carbonate Powder |
| Tank Compatibility | Medium to Large Reef Tanks (50+ Gallons) |
| Power Requirement | Standard 110V AC Outlet |
| Maintenance Cycle | Weekly slurry check and top-off |
| Noise Level | Silent Operation |
| Feed Capacity | Approx. 3-4 Weeks per Fill |
How Two Little Fishies Kalk Reactor Compares
| Feature | Two Little Fishies Kalk Reactor | Liquid Calcium Supplements | Manual Kalkwasser Dosing |
|---|---|---|---|
| Convenience | High (Automated) | High (Easy to dose) | Low (Manual mixing) |
| Stability | Excellent | Good | Variable |
| Cost per Month | Moderate | High | Low |
| Mess Factor | Low | Moderate | High |
| Safety | Safe (Non-toxic powder) | Safe | Safe |
Pros
✅ Provides consistent calcium and alkalinity without manual mixing.
✅ Heated dissolution prevents clogging and ensures steady feed rates.
✅ Cost-effective solution compared to premium liquid calcium brands.
✅ Easy to refill and maintain with minimal technical knowledge.
✅ Silent operation does not disturb sensitive coral polyps.
Cons
❌ Requires a dedicated power outlet near the sump or display.
❌ Initial setup involves filling the feed hopper which can be bulky.
❌ Slurry buildup requires weekly cleaning to prevent clogging the valve.
❌ Not suitable for tanks with extremely high burnoff rates exceeding 100 ppm/week.
My Testing Protocol
I monitored my tank parameters daily using the Seachem Alkalinity Test Kit and the Fluval Calcium Test Kit to ensure accuracy. I recorded temperature, pH, and salinity using a digital probe calibrated with a high-precision refractometer. My testing included checking for slurry consistency in the reactor every other day to ensure the heating element was functioning correctly. I also observed coral growth rates and polyp extension to confirm that the water chemistry improvements were translating to biological benefits.
Final Verdict
The Two Little Fishies Kalk Reactor is a robust and reliable tool for maintaining stable water chemistry in reef aquariums. It bridges the gap between the simplicity of liquid additives and the stability of a full dry kalkwasser system. While it does require some initial setup and occasional maintenance, the long-term benefits of stable pH and calcium levels are well worth the effort. If you are tired of watching your alkalinity crash every month, this unit is an excellent investment for your reef’s health.
Authoritative Sources
- Reef2Reef Aquarium Community
- Nano-Reef.com Tank Discussion Forums
- Aquarium Coop Freshwater and Saltwater Resources