Water change through a skimmer: how to remove antibiotics from water

Effective Removal of Antibiotics and Unwanted Substances from a Marine Aquarium

In a marine aquarium, there's sometimes a need to quickly remove unwanted substances—whether antibiotics after treating fish, chemical compounds accidentally introduced into the system, or residual lubricant from new filter bags. Many know that activated carbon can help in this situation, but it works relatively slowly and isn't always effective at high concentrations of unwanted substances.

When a Protein Skimmer "Goes Crazy": Signs of a Problem

One sure sign that unwanted chemicals are present in the water is abnormal protein skimmer behavior. It starts to "go crazy"—producing excessive foam that literally overflows from the top. The skimmer cup can fill within just 30 seconds, instead of the usual several days. This is not only unsightly (with splashes and droplets flying around) but also indicates a problem in your aquarium.

This skimmer behavior is especially common after:

• Using antibiotics (such as Chemiclean when fighting cyanobacteria)
• Installing new filter bags without pre-rinsing them
• Accidental introduction of substances into the water

Effective Solution: Water Change Through the Protein Skimmer

Instead of the traditional recommendation to perform a 30% water change (which for a 600-liter system means replacing 200 liters!), there is a much more effective method—removing the concentrated unwanted substances through the protein skimmer.

Preparation for the procedure

1. Prepare about 10-15 liters of fresh saltwater
2. Modify the skimmer for the procedure:
   • Many modern models already have a special hole with a fitting in the bottom of the cup for draining skimmate
   • If there's no such hole, you can drill one and glue in a fitting
   • Attach tubing to the fitting that will drain water into a bucket
3. Prepare a container for collecting water (a regular bucket from marine salt will work)
4. Turn off the auto top-off system during the procedure to prevent it from diluting the system

Process for removing unwanted substances

1. Place the drain tube from the skimmer into the bucket
2. Reduce the skimmer pump power to 20-30% of maximum—this allows you to control the water drain rate
3. Turn on the skimmer and observe the process—water with concentrated unwanted substances will begin collecting in the bucket
4. Gradually add the prepared saltwater to the system to compensate for the outflow
5. The process usually completes itself after 10-15 minutes, when the bulk of unwanted substances has been removed

It's important to understand that despite the apparent intensity of the process, you'll only remove about 10-15 liters of water from the total system volume, but significantly reduce the concentration of unwanted substances. This is much more effective than simply turning off the skimmer and waiting for carbon to slowly adsorb substances, for antibiotics to completely break down, or performing a huge 30% water change that won't give the same results as the method described above.

Comprehensive Cleaning: A Three-Stage Approach

For maximum effectiveness, a three-stage approach to system cleaning is recommended:

First Stage: Skimming

As described above, the main mass of unwanted substances is removed using the skimmer.

Second Stage: Activated Carbon

After changing water through the skimmer, place a bag of activated carbon in the system where there's strong water flow. The carbon will adsorb substances remaining after the first stage. This process happens more slowly, but now that the bulk of contaminants has been removed, carbon can effectively handle the residue.

Third Stage: "Coral Snow"

The final cleaning stage—using "Coral Snow" (pure, without additives). This white substance creates a cloudy suspension in the water when added, binding organic compounds and remaining contaminants. "Coral Snow" also helps "tame" the skimmer, which by this point should no longer be "going crazy" but may still be working more intensively than usual.

When adding "Coral Snow," the water temporarily becomes milky white but then quickly clarifies, becoming even more transparent than before the procedure. Contaminants bound to coral snow particles are removed through the skimmer in its normal operation mode.

Important Details and Recommendations

• Always rinse new filter bags with hot water before installation. They often contain silicone lubricant or other substances that can cause skimmer "craziness."
• When working with antibiotics (like Chemiclean), prepare in advance for the cleaning procedure described after completing the treatment course. Antibiotics can significantly affect biological processes in the system if not removed promptly.
• Don't be afraid of skimmer activity—if it begins intensively producing foam after adding new elements to the system, this is a normal reaction. Don't turn it off—instead, help it remove unwanted substances through the procedure described above.
• Monitor the water level in the system during the procedure and compensate by adding prepared saltwater to maintain stable salinity.

Why This Works

The effectiveness of this method is explained by the fact that the skimmer concentrates precisely those substances causing the problem. Instead of evenly diluting the entire system (as with traditional water changes), you purposefully remove a concentrated "broth" of unwanted substances.

Observations show that after such a procedure, the system restores its balance more quickly, and biological processes normalize much more effectively than when using only activated carbon or regular water changes.

This method is especially valuable for large systems, where a traditional 30% change would mean preparing and replacing hundreds of liters of water, requiring significant time and resources.

The combination of all three described methods—water change through the skimmer, using activated carbon, and "Coral Snow"—provides the most complete removal of unwanted substances from the system and rapid restoration of a healthy aquatic environment for your marine aquarium inhabitants.