Aquarium Medication Guide: Which Treatment for Which Disease

Quick-Reference: Disease to Medication Table

When your fish are sick, time matters. Use this quick-reference table to identify the likely disease and the most effective treatment. Always confirm the diagnosis before medicating — treating with the wrong medication wastes time and can add unnecessary chemical stress.

Common Medications Available in Singapore

Not all aquarium medications are easily found worldwide, but Singapore’s well-stocked aquarium scene means most major brands are available. Here are the key medications to know:

Seachem ParaGuard

An aldehyde-based treatment effective against external parasites, fungal infections and some bacterial issues. It is gentler than many alternatives and is one of the few medications considered relatively safe for scaleless fish when dosed carefully. Available at most aquarium shops in Singapore.

API General Cure

Contains metronidazole and praziquantel — a powerful combination that targets internal parasites, flagellates and flukes. Essential for treating hole-in-the-head disease and internal worm infections. Can be mixed into food for internal parasite treatment.

Waterlife Myxazin

A broad-spectrum antibacterial treatment from the UK, widely available in Singapore. Effective against fin rot, ulcers, body slime disease and other bacterial infections. Relatively gentle on biological filtration when used as directed.

eSHa 2000

A Dutch-made treatment that covers bacterial, fungal and parasitic infections in a single product. Popular for its broad effectiveness and relatively mild impact on filter bacteria. Available at many specialty aquarium shops in Singapore.

Hikari PraziPro

A liquid praziquantel formulation — the go-to treatment for gill flukes, skin flukes, tapeworms and other trematode parasites. It does not harm biological filtration, which is a significant advantage over many other medications.

Methylene Blue

One of the oldest aquarium medications and still one of the most useful. Excellent for fungal infections, egg care (preventing fungus on fish eggs), and as a short-term dip treatment. It will stain silicone, decorations and your hands, so use with care. Best used in a hospital tank or as a dip rather than in the main display.

Aquarium Salt (Sodium Chloride)

Not a medication in the traditional sense, but salt is remarkably effective against Ich, mild fungal infections and as a general tonic. Use pure aquarium salt or non-iodised salt — never table salt. Dose at 1-3 teaspoons per 4 litres depending on the condition being treated. Note: salt is harmful to most live plants and must never be used with sensitive species like corydoras or most shrimp.

How to Medicate Properly

Correct medication procedure is just as important as choosing the right product:

1. Confirm the diagnosis: Observe your fish carefully and research the symptoms. Misdiagnosis leads to ineffective treatment and unnecessary chemical stress. Refer to our common fish diseases guide for help identifying symptoms.
2. Remove activated carbon: Carbon will absorb most medications, rendering them ineffective. Remove carbon from your filter before dosing and do not replace it until the treatment course is complete.
3. Calculate the dose correctly: Dose based on the actual water volume in your tank, not the tank’s rated capacity. A 100-litre tank with substrate, rocks and driftwood may only hold 75-80 litres of water.
4. Increase aeration: Many medications reduce dissolved oxygen. Add an air stone or increase surface agitation during treatment.
5. Complete the full course: Do not stop treatment early because the fish looks better. Parasites and bacteria have life cycles, and incomplete treatment leads to resistant strains.
6. Perform water changes between doses: Most medications require a 25-30% water change before the next dose to remove spent medication and replenish minerals.
7. Re-add carbon after treatment: Once the course is complete, add fresh activated carbon to your filter for 48-72 hours to remove residual medication.

Dosing Tips for Singapore’s Warm Water

Medications often work faster in warmer water because parasites and bacteria have accelerated life cycles at higher temperatures. Singapore’s ambient temperature of 28-32°C means that Ich, for example, completes its life cycle faster than in temperate climates. This can actually work in your favour — heat treatment for Ich is more effective because the free-swimming stage (the only stage vulnerable to treatment) arrives sooner.

Medication Safety with Shrimp and Snails

This is where many hobbyists make costly mistakes. Most aquarium medications are harmful or lethal to invertebrates:

The golden rule: If your tank contains shrimp, always remove them to a separate container before medicating, unless you have confirmed the medication is invertebrate-safe. Copper is the biggest danger — even residual copper absorbed into silicone from a previous treatment can leach out and harm shrimp months later.

Hospital Tank vs Main Tank Treatment

Should you treat in the main tank or set up a separate hospital tank? Each approach has merits:

Use a Hospital Tank When:

• Only one or two fish are affected
• The medication will harm plants, shrimp or snails
• You want to avoid staining decorations (methylene blue)
• You need to use a medication that damages biological filtration
• You want to observe the sick fish more closely

Treat the Main Tank When:

• The disease is contagious (Ich, velvet) — all fish are likely exposed
• Multiple fish show symptoms
• The parasite has a free-swimming stage in the water column
• Moving the fish would cause more stress than treating in place

A hospital tank need not be elaborate. A 20-40 litre plastic tub or bare tank with a sponge filter (seeded from your main tank), a heater and a hiding spot is sufficient. The key is having one ready before you need it. Learn how to set one up properly in our quarantine guide.

Prevention Over Cure

The best medication is prevention. Most diseases appear when fish are stressed by poor conditions:

• Maintain water quality: Regular water changes and filter maintenance prevent the vast majority of diseases
• Quarantine new fish: Always quarantine new arrivals for 2-4 weeks before adding them to your display tank
• Avoid overcrowding: Stress from overcrowding suppresses the immune system
• Feed a varied diet: Good nutrition builds strong immune responses
• Match species to conditions: Fish kept in their preferred water parameters are inherently healthier

Frequently Asked Questions

Can I mix different medications together?

Never combine medications unless the manufacturer specifically states they are compatible. Mixing medications can create toxic chemical reactions, cause severe stress, or cancel out each other’s effectiveness. Complete one treatment course, perform a large water change, add carbon for 48 hours to remove residual medication, then begin the next treatment if needed.

Will medications kill my beneficial bacteria?

Some medications do harm biological filtration — particularly antibacterial treatments, which cannot distinguish between harmful bacteria and your nitrifying filter bacteria. Hikari PraziPro and API General Cure are generally filter-safe. After any medication course, monitor ammonia and nitrite levels closely for 1-2 weeks and be prepared to dose Seachem Prime if you detect a spike.

How long should I treat before seeing improvement?

This depends on the disease. External parasites like Ich should show improvement within 3-5 days of treatment. Bacterial infections may take 5-7 days. Internal parasites can take 1-2 weeks. If you see no improvement after completing the recommended course, reassess your diagnosis — you may be treating the wrong condition.

Where can I buy aquarium medications in Singapore?

Specialty aquarium shops carry a wider range than generic pet stores. Common medications like Seachem products and API treatments are widely available. For harder-to-find products like eSHa 2000, check dedicated aquarium retailers or online platforms. Visit Gensou at 5 Everton Park for expert advice on which medication to use — our team can help diagnose your fish’s condition and recommend the most effective treatment from our in-store range.

Dealing with sick fish is stressful, but having the right knowledge and medications on hand makes all the difference. If you are unsure about a diagnosis or treatment plan, do not guess — seek advice from experienced aquarists. Contact Gensou for professional guidance. With over 20 years of experience, we have seen and treated virtually every aquarium disease.

Related Reading

• Aquarium Medications Safe for Plants: What to Use and Avoid
• How to Treat Ich Without Medication: Heat and Salt Method
• Active vs Inert Substrate: Which Is Right for Your Planted Tank?
• Alternanthera Reineckii Care Guide: Bold Red Without CO2
• Alternanthera Reineckii Mini Care Guide: Compact Red Carpet Plant