Koi Ulcers: Causes, Symptoms, and a Proven 6-Day Treatment Protocol

Koi ulcers are not random wounds. They are the end result of parasites, stress, and bacterial invasion working together. Treating ulcers successfully requires more than killing bacteria — it requires creating a clean slate before bacterial therapy even begins. Part of our complete Koi Diseases & Treatment Guide.

This protocol reflects a professional, repeatable approach focused on eliminating parasites first, then applying controlled antibacterial treatment in a structured cycle.

What Is a Koi Ulcer

A koi ulcer is a full-thickness bacterial infection that penetrates the skin and exposes underlying tissue. Once the slime coat and skin barrier fail, opportunistic bacteria rapidly invade muscle and can enter the bloodstream.

Ulcers do not heal without intervention. Treating them incorrectly often makes them worse.

Why Ulcers Happen

Ulcers are almost always secondary infections.

The typical progression looks like this:

Parasites damage the slime coat and skin

Stress and water conditions weaken immunity

Bacteria exploit the damaged tissue

An open ulcer forms

If parasites are not addressed first, bacterial treatment alone is often ineffective.

Symptoms of Koi Ulcers

Common signs include:

Red, white, or open sores

Missing or lifted scales

Inflamed or bloody tissue

Localized swelling

Reduced appetite

Lethargy

Advanced cases may show:

Multiple ulcers

Pineconing scales

Red streaking

Rapid decline

Core Treatment Philosophy

Ulcer treatment fails when steps are skipped.

The philosophy behind this protocol is simple:

Parasites come first

Then controlled antibacterial exposure

Then reassessment, not endless dosing

This approach provides a clean slate, reduces reinfection, and allows the fish to heal between treatment cycles.

Proven 6-Day Ulcer Treatment Protocol

This protocol is designed for hospital or quarantine systems where dosing and salt levels can be controlled accurately.

Minimum treatment duration is 6 days.

Step 1 – Parasite Reset (Clean Slate)

The first step is eliminating parasite pressure and surface pathogens.

A Purple Magic treatment is performed to:

Strip parasites from the fish

Reduce surface irritation

Reset the slime coat environment

This step is critical. Treating ulcers without removing parasites often results in stalled healing or relapse.

Step 2 – Salt Support at 5 ppt

After parasite treatment, salt is raised to 5 ppt.

At this level, salt:

Reduces osmotic stress

Decreases fluid loss through open tissue

Supports slime coat repair

Improves tolerance to bacterial treatment

Salt is used as support, not as a cure.

Step 3 – Bacterial Blast Treatment Cycle

With parasites removed and salt stabilized, antibacterial treatment begins.

Cycle structure:

Salt maintained at 5 ppt

Bacterial Blast treatment for 48 hours

After 48 hours:

Perform a complete flush / 100% water change

Restore salt back to 5 ppt

Re-dose Bacterial Blast for another 48 hours

This process is repeated three times total.

Treatment Schedule Summary

Day 1–2:
Purple Magic → Salt to 5 ppt → Bacterial Blast (48 hours)

Day 3–4:
Full flush → Restore salt to 5 ppt → Bacterial Blast (48 hours)

Day 5–6:
Full flush → Restore salt to 5 ppt → Bacterial Blast (48 hours)

Minimum treatment duration: 6 days

Step 4 – Reevaluate After Day 6

After the third 48-hour cycle:

Reevaluate ulcer size and depth

Assess appetite and behavior

Look for reduction in inflammation and tissue exposure

At this point:

Improving ulcers may transition to recovery and support

Stalled or worsening ulcers may require escalation or extended care

Endless dosing without reassessment is not effective treatment.

What Not to Do

Do not treat ulcers without addressing parasites first

Do not shorten the treatment cycle

Do not skip full water changes between cycles

Do not overdose attempting faster healing

Do not mix random medications

Ulcer losses almost always come from rushed or incomplete protocols.

Prevention Moving Forward

Once ulcers resolve, prevention becomes the priority.

Key measures include:

Routine parasite control

Stable water quality

Proper quarantine of new fish

Maintaining slime coat health

Reducing stress during seasonal changes

Ulcers are preventable when the system is managed correctly.

Frequently Asked Questions

Why treat parasites first if I can already see bacteria?
Because parasites continue to damage tissue and reinfect wounds. Removing them first gives antibacterial treatment a chance to work.

Why use repeated 48-hour cycles instead of continuous dosing?
Flushing between cycles removes bacterial waste, toxins, and metabolites while preventing resistance and stress buildup.

Is 6 days the minimum?
Yes. Anything shorter is incomplete treatment.

Can this be done in a pond?
This protocol is best suited for quarantine or hospital systems where salt and dosing can be controlled precisely.

Final Notes

Ulcer treatment is not about throwing stronger chemicals at a wound. It is about sequence, control, and patience.

Parasites first.
Then bacteria.
Then reassess.

That is how ulcers heal.