FAQs on Freshwater Antibiotic, Antimicrobial Use Related Articles: Choose Your Weapon: Freshwater Fish Disease Treatment Options by Neale Monks, Understanding Bacterial Disease in Aquarium Fish; With a gallery of bacterial infections, a discussion of “Fish TB”, and a listing of major antimicrobial medications with examples available to fishkeepers By Myron Roth, Ph.D., FW Disease Troubleshooting, Freshwater Diseases, Nutritional Disease, Ich/White Spot Disease, Methylene Blue, Formalin/Formaldehyde, Malachite Green, Related FAQs: Freshwater Medications, Salt/Use, Aquarium Maintenance, Ich/White Spot Disease, African Cichlid Disease 1, Cichlid Disease,

Re: Redness near pectoral fins...
Antibiotics May Affect Biological Filtration 6/13/09
Hi WWW Crew, I checked the Internet and found that API (Aquarium Pharmaceuticals) is an American company. After browsing their website, I found that they too sell medications that are bio-filter safe. Products like Furan-2, Melafix, Pimafix, Tetracycline and Triple Sulfa does not hard bio-filter. So would you question the effectiveness of these API products since they claim that these are bio-filter safe? Have you had successful experiences with them? Regards, Roger
< Medications can say anything they want on the package. Bacteria convert ammonia to nitrites and then nitrates. Different kinds of bacteria attack the living tissues of aquarium fish. Is it possible for some antibiotics to be selective enough to only kill the bacteria attacking the fish? Sure it is. In your particular situation you have a fish with some redness around the pectoral fins along with some other symptoms. Are you satisfied with the results of treating with Interpet #9? If you are, then continue to treat as per the directions on the package. If not, then it hasn't worked.
I would recommend treating with a known antibiotic like Nitrofurazone or Erythromycin. Regardless of what they say on the package I would recommend treating in a hospital tank. If you have to treat in the main tank then I would still caution you about ammonia and nitrite spikes.-Chuck>

F/U Pics...Re: Fin rot... (RMF, opinion please)   2/25/09 Gentlemen, I've attached the some pictures, one of each fish. It may not be readily apparent, but the spaces showing in the Betta's tail aren't supposed to be there. So, I've also attached a picture of what his tail looked like when he was healthy. I appreciate all of the advice. Mr. Fenner recommended I use a Furan compound and remove the carbon from my filter. This prompted a question I've actually had for some time. I only use sponge filters. When I treat a tank with medication, I usually do a 25-30% water change at the end of the treatment, and then resume the normal maintenance schedule. Most of the instructions state to replace the carbon, which I know will pull the remaining med out of the water. Am I overdosing the fish if I don't have some sort of carbon removal system after a treatment? Should I do a larger water change, since I'm only using sponges? Again, thanks for the help. Laura <Hello Laura. The short answer is no, you aren't overdosing medications if you don't use carbon afterwards. Most medications are metabolised by the bacteria in the aquarium within a day, which is why most require a series of doses across a period of several days. That's the only way to expose the fish to a continual amount of medication. When you've finished treating with one course of medications, doing a 25-50% water change is a good idea, but by the next day, you should be good to go with a new course of medications. Cheers, Neale.> <<Agreed. RMF>> Re: F/U Pics...RE: Fin rot... (RMF, opinion please)  2/25/09 Thanks. Were the pictures helpful to you in trying to identify whatever's going on in my tanks? Laura <Nope. Sorry. The reality is that most viral, bacterial infections can only be identified under the microscope. Just as with humans: if your doctor thinks you have an infection other than one of the really common and obviously (and often, even then) blood tests, urine samples and so on will all be required. The same with fish. Most of the time I'm dealing with same infections that plague virtually all tanks at some time or another: Finrot, secondary Fungal infections, Lymphocystis, etc. But if the symptoms fall outside that range, it's out of what I can do. Cheers, Neale.> <<Nice pix, but indicated nothing to me (hence I did not post ayer). RMF>>

Re: Fin rot... (Bob, need your input re: Furanace)– 02/28/09 Sorry to be a bother, Furanace says it will harm the bio-filter and a Q tank is recommended. <Have not used this so can't comment myself. Have asked Bob to chime in here.> <<Furan compounds can indeed interrupt nitrification... Ammonia et al. need to be monitored, freshwater prepped, stored for use... RMF>> So I've moved the guppies to a Q tank and I'm treating there. I only got the adults, not the fry. But I'm wondering if the "disease" is in the water of the display tank, and if I should assume the fry are infected? Because we think this spread from my guppy tank to my Betta tank on "something wet and unsterilized". Do I have to treat the main tank in order to make sure everyone gets and stays better? <I would imagine that this would be essential. <<Yes>>Treating the adult Guppies in a quarantine while maintaining a reserve of infectious bacteria in the fry in the display tank would defeat the object of the exercise.> I REALLY don't want to recycle this tank "fish in" if I can avoid it. Thanks again for all the advice. Laura <Cheers, Neale.> Re: Fin rot... (Bob, need your input re: Furanace) 2/28/09  Thanks. So, if I remove all fish from the display tank, I will remove the infectious bacteria while preserving the bio-filter? Laura <Hi Laura. I'd imagine that even if you treated the fish in a quarantine aquarium, there'd be no guarantees that the infection cycle would be broken in the display tank. The problem is that bacteria *aren't* like protozoan parasites. If you're treating Ick parasites and you remove the fish to another tank, then any free-living Ick parasite "juveniles" in the display tank will only have 24 hours (approximately) to find a host. If they fail to do so, they die. Within a few days, you'll break the infection/re-infection cycle. But bacteria are notoriously good at going dormant. That's good in some ways: it's how nitrification bacteria spores in the air and in water are able to land in a new aquarium, set up home, and get your filter running. But on the downside, disease-causing bacteria could potentially do the same thing, resting up in the gravel or water column until such time as a suitable host came along. So while treating your fish in a quarantine tank with a zeolite ("ammonia-remover") based filtration system would be wise, you'd still need to dose the main tank too. I'd keep adding a bit of food to the display tank, so that as it rotted, it would produce ammonia for the filter. If after X days of treatment (where X is the recommendation on the Furanace package) you found zero ammonia in the display tank, you would be safe to assume the filter survived the antibiotic treatment, and you could return your fish. Check the ammonia or nitrite levels every couple of days, and put the fish on half-rations. Essentially what you'd do if you were adding fish to a recently-cycled aquarium. As for the quarantine tank, all you'd need there is a box filter or similar filled with zeolite. If you have two filters on the display tank, you can use one of them here, emptying the biological media compartment and filling it with zeolite. Don't feed the fish while treating unless the course is 7+ days. Or if you must feed the fish, as you might in the case of fry, use vegetable foods exclusively, as these are much lower in protein. Sushi Nori would be ideal and is readily consumed by poeciliids (and likely much healthier than flake!) Re: Fin rot... (Again Bob, comments appreciated) <Zip to say. RMF> 2/28/09  Got it. I was afraid of that. Any ideas on how this happened? You may remember, I'm the one who's fairly Obsessive Compulsive about regular tank maintenance. Thanks again. Laura <No idea. Could be bad luck: introducing new fish for example, or the infection could by a bacterium ubiquitous to aquaria (like Aeromonas and Pseudomonas spp.) that only causes problems under specific situations. Bacterial infections that resemble Fish-TB are almost a problem in freshwater tanks where inbred fancy fish are being kept: Guppies, Ram cichlids, Dwarf Gouramis, etc. So genetics probably plays a role. Cheers, Neale.>

Mardel Tetracycline has filled my tank with foam  9/11/08
Hello
We have just finished treating two fan-tail calico fish for fin damage with Mardel Tetracycline. We have treated for full five days, added carbon filters back to the tank after a 25% water change,
<Mmm, you'll have to change out more water than this>
as the directions have stated. The fish look great, but now our tank looks like a sewage plant. We have reddish brown nasty water with a giant marshmallow-like foamy substance across the entire surface of our tank. We have four (4) aeration devices, that is probably contributing to this problem.
<Yes>
Long story short... we want to get rid of the foam. We do not understand how the filters are suppose to help this if the foam is on the surface and lingering. The color of the water has changed slightly within the 24-hours since the filters were put back in. We believe that the color will get better. But is there anyway to get rid of this horribly disgusting foam??!!
<Yes... two things... clean/white (non colored) paper towels draped along the top to absorb most, and dipping a pitcher in at an angle to remove the surface material... And time going by otherwise>
Our return e-mail address is XXXX. Thank you very much for your time and knowledge.
Sara and Jamie (humans), Pirate and Zombie (Our two calico fans)
<Happy to share. Bob Fenner>

Nitrofurazone... use, effect on nitrification   2/14/08
Looked all over your site for the answer?
<You did?>
let me start at the beginning, I've seen collectors using Nitrofurazone (yellow water) to store recently collected fish. In some cases I've heard of wholesalers using it to fend off disease.
<Yes... not uncommon with FW...>
Question
Is this a good idea to use constantly in a quarantine tanks for all new arrivals
<Mmm, not IMO/E>
Will it affect the biological filter? (a little) (a Lot)
Fred
<Furan compounds generally do not affect nitrification (directly), but can do so in established, closed (e.g. hobbyist) systems. Bob Fenner>

Hospital tank filtration with antibiotics   7/29/07
<<Hello, Geri. Tom here.>>
I can't seem to find an answer to the following dilemma: I understand that the biological filtration should be established first when setting up the hospital tank. However, as soon as antibiotics are added as a treatment for a diseased fish, doesn't the biological filter get wiped out?
<<A valid question and a good one. Antibiotics can, and will, damage/destroy the bio-colonies established in our hospital tanks and their filters. These medications are indiscriminate about which bacteria they go after. Bear in mind, though, that there are antibiotic medications that “kill” bacteria (bactericides) and others that inhibit reproduction/growth of bacteria (bacteriostatics). It’s incumbent upon the hobbyist to make the appropriate choice based on the disease the fish is/are being treated for.>>
Then what happens to the ammonia and nitrite that builds up in the tank?
<<Let’s look at this one from a realistic viewpoint. How much ammonia is going to be produced by a sick fish? (Not being sarcastic here at all, by the way.) The amount it eats will be minimal, at best – and you should feed it with that in mind. Ammonia will be excreted through the gills as the fish breathes but, alone, this shouldn’t present a big problem in terms of water toxicity as long as you practice the proper maintenance of the tank. There are two points to keep in mind where “hospital tanks” are concerned. First, you’re, hopefully, treating a single fish outside of the display tank, i.e. the remainder of your livestock will remain unaffected by any adverse reactions to the medication(s). Second, not all “hospitalization” requires antibiotics. Your pet apparently does but, there are many reasons for treating fish in a separate aquarium that don’t carry the same “baggage” that you have to deal with now. In short, you’re concerns are specific to you, and rightly so, but they’re not common to the whole concept of “hospitalization.”>>
I know partial water changes should be done daily or every other day in this situation but even a little ammonia and/or nitrite is hazardous.
<<True enough but consider which “condition” is primary and which is secondary. Hazardous as the ammonia/nitrite toxins can be, these can be controlled through water maintenance/changes. Concentrate on treating your pet, first, and, with a proper regimen, the other concerns will take care of themselves.>>
Lastly, why even start up the biological filtration to begin with if it just gets wiped out?
<<As I stated previously, not all hospitalization requires the use of antibiotics. Many treatments in a hospital tank have no effect on the beneficial bacteria whatsoever. I’m afraid you’re looking at the “concept” from a narrow perspective. I completely understand it, under the circumstances, but you have larger issues to deal with right now.>>
Help, my angel is dying and I must get him to the hospital!
Geri from Newton, MA
<<Do it, Geri, and stay on top of the water changes. Best of luck. Tom>>

Could Maracyn Make a Fish Sick/Red Streaks? Mmm, yes. Goldfish misplaced in a ten gal. sewer    6/18/07
I have had my goldfish for nearly 3 years. About 2 weeks ago, I noticed his fins have been fraying on the edges, but no red streaks and good appetite.
<Likely environmental...>
But it's true - he's about 6" long and in a ten gallon tank
<... def. env.>
with good Marineland filter, but he needs more space. He's been in this tank for 2 years and has been sick before - I brought him back from a bad case of septicemia a year ago with Maracyn 2 and the homeopathic remedy belladonna 30C potency. No other fish in the tank.
<...>
So earlier this week, I did a 50% water change - readings were regular "normal": before hand:
<...>
7.9 PH, 0 ammonia, 0 nitrite and some what high nitrate of 40
<Toxic...>
(the water here is heavily buffered so PH is naturally high and the nitrate comes out of the faucet at 10, so hard to get it lower.)
<I would NOT consume this source water myself... see WWM re>
I added Maracyn.
<For?>
The tank got cloudy after the 3rd dose and he seemed lethargic. Fourth dose was yesterday evening, but today we noticed big red streaks in his tail and that he was sitting on the bottom with his fins closed. I did another 50% water change, put in a new filter, added Cycle
<Not worthwhile>
to boost the beneficial bacteria, but the last thing I expected when I decided to add the Maracyn was that he would get worse. He is swimming around in his usual lively fashion right now after the latest tank care, but I think the Maracyn did something to bring on the streaks. When I used it last year (to no effect) and then the Maracyn 2 to deal with the septicemia, it did not turn the tank cloudy. I plan to try the homeopathics again after a couple of hours for the tank to run. At the moment, I am loath to give him more antibiotics.
Suggestions welcome.
<Good speculation... An antibiotic can have such an effect... not-so-selectively killing off microbes... But the real issue here is overall health... and your system is just too small to accommodate this one large goldfish... as evidenced by the hemorrhaging, the high accumulated Nitrate (and much more)... What you really need to do is read and heed here: http://www.wetwebmedia.com/FWSubWebIndex/gldfshsystems.htm
and the linked files above. Bob Fenner>

Getting Erythromycin For Infected Toad  – 2/25/07
Can you tell me where I can find erythromycin?
< Any good tropical fish store will have this or a derivative.-Chuck>

Using Oxytetracycline
Good day!  Just thought I should say your website has been a great help, and a good thing to browse through. Also, I need to ask about a medication I'm using for my fish. I have a thirty gallon tank with some angels, mollies, betta, snails, live plants, and one platy.  (Sounds a bit crowded, doesn't it?  I'm planning to get a larger tank for the angels very soon, so no worries there.)  Anyway, I had a few guppies in there, but just a few days ago I noticed that the male had started to swell. I'd previously had a female betta develop dropsy, (to my horror, of course) so I knew what to look for, and how the symptoms played out.  I separated him into a small quarantine tank, added a bit of Melafix as a buffer, and kept the water as clean as I could for the last two days.  Today I was asking my mother about going and getting some Epsom salts or some fish meds (which are particularly hard to find in my town), and I told her what I had read about for treating dropsy in guppies.  She said that we had some oxytetracycline I could use.  We have a cattle ranch, and use the medication as an injection for infections.  So, figuring out the dosage from 1/4 teaspoon per twenty gallons of water, I treated him just a couple of hours ago.  He's been swimming around very well even though he's been infected, so I'm not too worried about him.  He's a tough little fish, and he's lived a good life, and I'm doing what I can for him.  If he's destined to get better, then he will.
Anyway, my real question is, if this treatment works, (which I'm hoping desperately that it does), then can you tell me a bit more about oxytetracycline and using it in my big tank?  Is there anything you'd suggest against?  I'd like to keep my plants and snails healthy and in the same tank, so I'd move the fish if necessary.  I've scoured the Internet for information on its affects towards my thirty gallon's inhabitants, and found nothing.  So I was curious that if I were to add it into my large tank as a buffer, or as a treatment as needed, would I need to do anything special to the tank?  (example, remove filters, remove plants, so on and so forth.)
Your help is greatly appreciated! Thanks,  Kati
< About 20-30 years ago this was the big antibiotic for South American fish coming into Los Angeles. It turns the water blood red and is pretty ineffective in hard alkaline waters. Now after saying this. Stuart Grant who live on the shores of Lake Malawi in Africa use this medication on his cichlids. He uses a dosage much higher than what is recommended from the manufacturer. So I guess you can overmedicate to get some curing effect but I would not try this around here. A better way to treat your betta would be the following. Do a 50% water change, clean the filter and vacuum the gravel. Organics affect the medications ability to treat diseases. Treat with Metronidazole and Nitrofurazone or Clout. Add some salt to the water and make sure the water temp is up around 80 F. All medications will have an affect on the good bacteria needed to break down fish waste so watch out for ammonia spikes.-Chuck>

Baths for freshwater fish?  9/18/06
Hi Bob,
Once again fighting tail rot in Betta Terrence. Doing my best to keep the water quality good with frequent small water changes, gravel vacuuming, the tedious process of wicking the dissolved solids off the surface of the water with paper towels, light feeding, etc... He's in a 2.5 gallon heated, filtered tank with 10 watts of fluorescent lighting.
As the tail rot has been persistent, I'm thinking of treating him with an antibacterial.
<Yes, this is what I would do. Likely... Oh, I see this below>
I was wondering if, instead of treating the whole tank, I could give Terrence a bath in the Nitrofurazone/Furazolidone/potassium dichromate medication that I've used before. Same dosage/concentration as for a full tank treatment?
<Yes>
(I read up on dips/baths on WWM, but only found info about dips/baths for marine livestock.
<Are more useful for marines... as they "drink" their environment, but can be used with good purpose on external complaints of freshwater aquatics>
I have heard from other sites of saltwater baths for FW fish... would that be more gentle/any more effective than an antibacterial?
<Mmm, not as much here>
He has Doc Wellfish's salt in his tank all the time, 1 tbs/5gal.)
If this would be ineffective or a bad idea, I can certainly treat the tank. I have an extra sponge in there that I can pull out and maintain in a Tupperware container to keep some good bacteria going. Just wasn't looking forward to dying the tank green and wiping out my filtration,
<Yes... I would use the immersion bath instead here as you state>
plus I anticipate the gravel will absorb some of the medication.
<You are correct>
Thanks for any insight you can give!
Rachel in NC, where it's finally cooling down a little
<BobF in sunny S. Cal., with a persistent cough/cold!>

Re: Baths for freshwater fish?  9/18/06
Bob,
I just did what I realized was the obvious thing to do... put Terrence in the 3/4 gallon Tupperware with a heater and a proportionate amount of medicine.  Planning on doing large, possibly complete, water changes every day or every other day.  So never mind about the bath!  Sorry to bother you.  It seemed like such a brilliant idea at the time!
<Is a good idea. BobF>

Gar With Sores On His Head  - 09/07/06
I have a spotted gar that has developed some type of disease. It has white film and ulcers, deterioration, on it's head. I have been treating it with Maracyn-two. Following the directions for the 6 day treatment. Not much improvement. Since their skin is not the typical fish type, would this be the correct treatment? Also, by putting aquarium salt for freshwater fish in the tank harmful to him? Could this cause a problem. Thanks.
< Gars are actually pretty tough critters. There could have been some damage to his head as he tried to jump out and now they got infected. I would try Nitrofuranace. It treats a wider range of parasites and it also has some antifungal properties. Salt wouldn't harm him unless it was an unusual amount. Do a 50% water change, vacuum the gravel and clean the filter. This medication may harm the good nitrifying bacteria so watch for ammonia spikes.-Chuck>

Maracyn Treated Tank 7/22/06
Hello...
<Hi>
I have added Maracyn to cure a supposed gill disease in my 29 g fw tank.  I pulled out the carbon, and noticed
my water is getting foggy.  Is this common for this broad spectrum. antibiotic?
Thanks!  
Jenn
Tony
<The tank is getting cloudy because it is recycling.  Most likely the Maracyn nuked your biological filtration.  The cloudiness comes from the unprocessed biological materials and to some degree the recolonizing bacteria.>
<Chris>

Furazone-green    6/4/06
On the advice of my local aquarium shop, all of my new fish are put in a quarantine tank for 15 days. I put one fish only in a 10 gallon tank at a time. I use the water from my 125 gallon tank to get it going. There is plenty of aeration and I monitor the  ammonia levels and do a 25% water change every other day.
<Well done!>
I put one capsule of Furazone-green in for the first 7 days only then leave the fish there for the next 8 days. Am I doing the proper thing for the fish trying to be preventive with the medication or am I doing harm, or better off doing nothing in reference to the medicine.      Thank you, Tony
<This product is used by many folks in the freshwater livestock trade as a standard practice. Is quite effective, non-toxic... In businesses where it has been a matter of my discretion, I have used it routinely... seems to act as a sort of gentle anti-microbial, dyes the water a bit, providing a calming effect... Bob Fenner>
 

Furan compounds - 03/14/2005
I must ask one question if I may.  Where does one fine Nitrofuranace?  I have looked all over the internet and I would love to have some on hand just in case it is needed.  I didn't know you had a post until just now, and I am not sure how to post on it if/when need to ask for advice.
Thank you again.
Lesley
<Ahh, search for either Nitrofuran or Furanace... or even "Furan compounds".
Bob Fenner>

Getting Good Medication  9/7/05
Thanks for advice. You'll find it pretty funny but our pet stores don't have any medicines for treatment of disease. Can I use erythromycin that is used for humans.?
< No. Go online to DrsFosterSmith.com. You will find everything you need there.> <<Actually... there is no difference in "pet-fish" antibiotics and those for humans. RMF>>
If, yes then in what amount and for what time? Should I add to tank or keep
them in separate tub or container containing that medicine.
I shall be grateful to you if you solve my problems.
< Hospital tanks are always better than treating the main tank. Check out articles and FAQ's about quarantine tanks too.-Chuck>

White slime coat
What is a very fine white sheen that seems to be in the slime coat and seems to only cover portions of body?
<Possibly a bacterial infection, perhaps a reaction to poor water quality... rarely a true fungus>
I know ich and it is not that. I lost 20 cichlids in my 150 gallon tank with sump and gravel filtration. It was stocked with electric blue, a variety of peacocks, and red empress which were over a year old that I had raised together since they were 1" fry. One day I noticed a white spot on the eye of a female red empress. It grew larger the next day, so I checked with the LFS and they gave me Amoxicillin for Popeye. I gave four treatments every other day over seven days. The eye cleared up at the end of treatment, but most of my cichlids developed a very fine white sheen over parts of the body, mostly on the side of the body and some had it around the head also. Ph was 8.0, Ammonia was .5 ...
<This is definitely a problem... toxic by itself at this concentration... the antibiotic killed off your nitrifying/biological filter>
...and the fish were hanging at the top of the tank and had a very poor appetite. I put my carbon filter back, did a 30% water change and added Amquel to remove ammonia. The next day the fish began eating and acting fine again, but the white sheen continued. Two days later the Ammonia went up to 1.0 
<... yes, the fishes continued to produce/excrete ammonia...>
and the pH dropped from 8.0 to 7.8. I vacuumed the gravel and added stress coat. The next morning all 20 of my 3-4" beautiful cichlids were dead on the bottom of the tank. I checked the ph and it was 7.4 with ammonia at .5. My tap water is 7.6 from a well. I'm sure the pH change and obvious crash of the tank killed the fish...
<Yes, I agree>
...but I don't quite understand what caused such a drastic pH change and would love to know what the fine white sheen was?
<All likely related... the pH drop was consequent to general decomposition of the dying filter biota, fishes... the sheen a chemical reaction of your fishes to the high ammonia, drop in pH... bought on mainly by the antibiotic killing off your bio-filter>
Side note: They did extremely well all year with many females reproducing. I cleaned out all the dead fish, rocks and plastic plants; surprise of all there was one little peacock fry swimming at the surface. He is now in another tank with all the fry produced from this tank of cichlids. 
<Am sure you see the logic now of not treating ones livestock in their main/display tanks, and the meaning of the word "anti" (against) "biotic" (life). Bob Fenner>