Seachem KanaPlex is a kanamycin-based aquarium antibiotic widely used to treat bacterial infections in freshwater and marine fish. Kanamycin is an aminoglycoside with broad-spectrum activity against many gram-negative and some gram-positive bacteria, making it a go-to medication for fin rot, dropsy, columnaris, and septicemia in hobby aquariums. KanaPlex is sold as an over-the-counter aquarium product, not a prescription-grade veterinary medication. Recent FDA regulatory changes have shifted the availability of aquarium antibiotics, and some keepers may have difficulty sourcing kanamycin depending on region. For valuable fish, always consult an aquatic veterinarian.

Overview

Kanamycin works by binding to the bacterial ribosome and inhibiting protein synthesis, which is lethal to susceptible bacteria. Unlike many other fish antibiotics, kanamycin is absorbed through the gills, which means it can treat systemic bacterial infections through water dosing — a valuable feature when fish are too sick to eat. KanaPlex can also be bound to food with Seachem Focus for direct gut delivery.

Uses

  • Bacterial fin rot
  • Dropsy (when bacterial cause is suspected)
  • Septicemia (red streaking, ulcers)
  • Columnaris (cotton wool disease)
  • Popeye (bacterial form)
  • Mouth fungus (often actually columnaris)
  • External and some internal gram-negative bacterial infections

Dosage

  • Water dosing: One level measure (included scoop) per 5 gallons every 2 days, for up to 3 doses (6 days total)
  • Food dosing: Mix 1 measure KanaPlex with 1 measure Seachem Focus per tablespoon of food. Feed for 5 to 7 days.
  • Combined: Water and food dosing can be used together for serious infections
  • Perform a 25% water change before redosing

Always follow the product label for exact dosing.

Safety Considerations

  • Reef-safe and invertebrate-safe — KanaPlex is generally considered safe for corals, shrimp, and snails at label dose, one of the few antibiotics usable in reef systems
  • Scaleless fish — Generally well-tolerated in scaleless species
  • Biological filter — KanaPlex can have some effect on nitrifying bacteria. Monitor ammonia and nitrite during treatment.
  • Hard, alkaline water — More effective in slightly alkaline water; activity is reduced in very acidic conditions
  • Fish kidney effects — Aminoglycosides can be nephrotoxic at high doses; follow label strictly and do not exceed recommended treatment duration
  • User safety — Wash hands after handling. Wear gloves if you have sensitive skin.
  • Regulatory status — Availability of kanamycin as an aquarium product may be limited depending on region due to FDA enforcement actions

Water Chemistry Effects

  • Minimal effect on pH, hardness, or salinity at therapeutic dose
  • Activated carbon removes kanamycin — remove carbon during treatment
  • Some effect on beneficial bacteria; monitor ammonia during extended use
  • Stable in most aquarium conditions

How to Use

  1. Test water and perform a water change if parameters are off
  2. Remove activated carbon from the filter
  3. For water dosing: dissolve one scoop per 5 gallons in a small amount of tank water and add to the tank
  4. For food dosing: mix with Seachem Focus, bind to food, and feed daily
  5. Redose every 2 days for up to 3 doses
  6. For serious systemic infection, combine water and food dosing
  7. After treatment, perform a 25% water change and return activated carbon

FAQs

Is KanaPlex reef-safe? Yes, it is generally considered safe for reef tanks and invertebrates.

Can I use it with MetroPlex? Yes, KanaPlex and MetroPlex are commonly combined with Seachem Focus for fish with multiple infections or hole-in-the-head disease.

Will it damage my biological filter? KanaPlex has some effect on nitrifying bacteria but is generally tolerated at label dose. Monitor parameters during extended treatment.

Does it treat ich? No. KanaPlex is an antibiotic and does not affect protozoan parasites.

Can I overdose my fish? Aminoglycosides can be nephrotoxic in large doses. Follow the label strictly.

Do I need a prescription? In some regions, regulatory changes have affected the availability of aquarium antibiotics. Check your local market.