Medicine Contraindications

Aquarium medication ingredients:

First of all, please take a look at the ingredients in your medication. Since there are soooo many meds out there it is impossible for us to list and keep up with new ones and every one. It is the owner's responsibility to check the packet for ingredients and expiry date. Most fish meds will contain a combination of the ingredients below and under law all should be listed.

Secondly, there is a list of medications Andrea and others compiled in Treatments, please refer to that in tandem as it contains usage directions and other useful points not covered here.

Third, while medications can be useful and life saving if chosen carefully, sometimes we are apt to use the wrong one (or wrong dosage or with other contraindications present) and this can harm the fish. A good plan to avoid this is to list all the symptoms your fish has and consult Mods/helpers/other members and similar case threads for best diagnosis and choice of meds, paying special attention how to use them. Remember, in the case of all meds used -any stressors like low dissolved oxygen, changing or acidic pH or any ammonia present can be a lethal combination worse than the disease itself sometimes. Always water change and then check params+ pH before adding meds.

Remember too, the more active ingredients in the medication (number of) the more potentially dangerous or powerful the medication usually is.


Sooo many precautions, not for the novice. Use gloves. Keep in well ventilated area. In the dark. NEVER in fridge. Removes 70% of DO in water so weak fish may die of suffocation. Huge increase of toxicity at high temp above 70F.

NEVER use any product containing formalin with salt, it is toxic. Do not use with salt.

Formalin can sterilize bettas and smaller fish.

NOT effective on bacteria, only ectoparasites. Kills many bbs.

Malachite Green. or any other so called greens (e.g: aniline green, basic green 4, diamond green B, Victoria green b etc). Also a registered carcinogen and banned for use in fish food fish. Toxic dye, toxicity related to pH, temperature and DO levels. More toxic in high pH. Does kill bacteria as well as parasites. Kills all bbs. Higher dose needed for marine tanks. Loaches and tetras need just half doses. Do not use with high levels of salt.

Acriflavine: Can sterilise fish. Top breeders do not use it for high quality potential breeding fish.. It's a disinfectant, a dye. It can be used with 0.3% salt which is an advantage but it will wipe out all bbs. They are very sensitive to it. Can also be mixed with green and/or copper.

Meth Blue. . Used in many topical applications. Again all the precautions of the other toxic dyes. Kills bacteria and parasites.

Can be used with salt. Can be mixed with most other meds inc. antibiotics.

Many have used this to good effect and it can be very effective and is the best treatment for velvet BUT coppper can NEVER EVER be used in acidic or fluctuating pH. It can kill fish very fast in soft or low kH water. Works on parasites mainly. It is immunosuppressive so should only be used on fish that are active and not really really sick. Cannot be removed well with carbon and should be removed via a 100% water change.
Not to be used in reef tanks/with salt or with snails.

Toxic if used past expiry date be careful to check the date.

Melafix: Tea tree oil and Pimafix: West Indian Bay tree oil:

Can be used with anything. But never longer than 8 consecutive days. These are oils so some say can clog gills and extensive use should probably be avoided if fish has weak or impaired gills.

Absolute contraindications ; antibiotics.

Tetracyline antibiotics in the water should not be used with salt or in high gH.

Salt and high gH makes them ineffective because tetracyline binds with calcium and magnesium making them inactive.

They are ineffective in high pH/over 7.5.

Tetracylines should be used alone and not mixed with any other meds (except in med food and *).

Maracyn 2/minocyline is a synthetic tetracyline.

Tetracylines can cause anemia.

Maracyn 2* can be mixed with Maracyn/erythromycin.

No other tetracyline meds should be mixed with other antibiotics in the water.

All tetracylines are light sensitive and will turn the water brownish as they decompose. Water should be changed if you see this happen and the tank should be covered and in dim side light only when using..

Minocycline should not be used with Medigold food but can be used with Metromeds..

Eryhthromycin/Maracyn treats mostly gram positive bacteria and is not well absorbed in the water. It can be administered by injection or in food and can be used with minocyline (and with rifampicin to treat mycobacter/fish TB).

Erythromycin should not be used with Medigold food but can be used with Metromeds..

All other antibiotics used for goldfish can generally be used with low salt. Some antibiotics like Kanamycin are actually more powerful

and effective when used with low salt. However, remember that salt is not necessary with antibiotics that are chosen and dosed accurately and can be an extra burden on fish and bbs. Salt should not be used in fresh water aquariums on a regular basis.

Using zeolite/ammo chips and nitrazorb

When using any of these do not use salt. Salt will release toxins back into the water.

Epsom salt:

Can be added with anything at the low recommended dose of 1/4 teaspoon per 10 gallons.

In certain special and rare circumstances it can be used with regular salt.