Gram negative columnaris bacteria can invade the gills and cause “gill disease”. The gills become red or brown and inflamed, there can be spots of red at the base of the pectoral fins and a thin papery look is found on the gill plate due to mucus. The fish hangs in the water and “pants” in obvious distress. This is a serious disease. The swelling, lack of distinct gill structure (“mashed” appearance), and red hemorrhagic areas (aneurisms) next to white necrotic (dead) gill tissue cause the gills to look like raw hamburger meat.
This disease often comes after an attack by a protozoan like ich or chilodonella on the gills of the fish. This secondary invasion is much more serious than the primary protozoan infection. The most common outward appearance of gill disease is the appearance of red spots at the base of the pectoral fins; Here are some examples of that:
This is most often gram-negative columnaris bacteria. It should be treated with broad spectrum antibiotics (Midland Vet Service Aqua-Mox, VetDepot Amoxicillin, Fishbiotic Ampicillin, Mardel Maracyn 2, SeaChem KanaPlex, API Fin And Body Cure).
Bacterial infections are most effectively treated with antibiotics in the food. Many believe (and the instructions on the antibiotics say!) that antibiotics need to be added to the water. They are simply incorrect. This controversial topic is covered in the following link:
12.5. Fish Don’t Drink
It is easy to make medicated food. Heat 1/4 cup water (two ounces or 58 milliliters, not a lot) in the microwave. Then blend seven grams of plain animal derived gelatin (Knox gelatin, one packet) into the hot solution with vigorous stirring. Take two tablespoons of dry commercial fish food (pellets or flake) and mix it with just a little of the hot water/ gelatin mixture. Add hot water/gelatin until you get a paste like consistency. If it gets too watery just add more food. To get gel food to float simply mix in a little whipped cream at this point.
Then add just a “smidgen” (roughly 1/16 teaspoon, a 1% to 2% addition) of medication to the mud. If you are using more than one medication mix the medications together, then use just a “smidgen” of the mixture. If you are using a packet of medication, take just a “smidgen” of the packet contents. Mix and mash the whole mass thoroughly. Spread it out into a pancake about 1/8th inch (3 mm) thick on a plastic film or a plate. Then put in the refrigerator. If you plan on keeping it for more than two weeks put it in a small plastic bag and freeze.
All the fish in the aquarium should be fed a steady diet of the antibiotic laced food for at least ten days. The entire aquarium should be treated even if the symptoms are only on one fish. This disease is a rapid killer and all the fish exposed to it need to be treated. Note that the exact amount of medication which goes into the food is not very important. Antibiotics can be overdosed pretty much with abandon as they are only toxic in large doses over a period of months. Note antibiotics in the food do not affect the filters so they can be left in place and operating.
If you can’t resist the urge to treat the water, remove the biofiltration media (including sponge and/or foam) in the filters and put it in an open container for the duration of the treatment. Sometimes antibiotics kill the beneficial bacteria and sometimes they don’t. In any case the filter media will denature the antibiotics. Monitor the ammonia and would do a 50% water change if it spikes above 1 ppm. Reduce the amount of food fed by 2/3 rds.
Note that if antibiotics are not available, it is quite easy to take a pill or capsule of human antibiotic and use it for fish. If it is a pill just grind it up. Just be aware that the human antibiotics are about ten times more potent than the aquarium antibiotics, so just a “smidgen” in the food is more than enough. This is a very good option for the folks in Europe or Canada, where fish antibiotics are illegal.
Note that fish with no pigmentation (i.e. albinos) tend to have very red gills as there is no pigment in the gill covers. The various glofish all have very red gills. These fish are not sick and do not need treatment.
The entire topic of bacterial infections in tropical aquarium fish is covered in more detail in this link:
10.3.11. Treating Bacteria
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