Antichton

Hmm, I would expect to see more than just a couple isolated fish at a time displaying symptoms if oxygen is low though, right? I don't have any airstones in the tank, but I do have 2 HOB breeder boxes that are driven by air. I can turn up the air flow on these boxes. Alright, I'll give this a shot!

Not that I can see; most of my fish are still eating well. I'd take a picture but no one is pooping right now....

I suppose this is a lesson in quarantining new fish.... So I recently bought a few clown killifish from the LFS. They came in super tiny (around 1/4" long). I drip acclimated them to my water and put them in a breeder box so they wouldn't get eaten by my larger fish. One week later, 4/5 I bought are doing great (I lost one to a swim bladder issue that developed after 3 days). I was pretty happy with the ones I bought and wanted to round out the school, so I went back to the store and bought 6 more. 1 week later, and I've lost over half of the killies. To my eyes, they look fine on one day (eating and swimming normally), and then I wake up the next day to find 1 or 2 suffering from a swim bladder issue (either floating at the top or wriggling at the bottom). The fish with swim bladder issues died the next day. Normally, I'd just think of this as a bad batch or weak fish, but 3 days ago, one of the dying clown killies slipped through the grate in my breeder box and one of my gardneri killifish ate it. 24hrs after that fish ate the dead fish (2 days ago), it became lethargic and a 2hr after that started suffering from swim bladder issues. Furthermore, 2 of my 2yo clown killifish school and 3 of my guppies have died under similar circumstances over the last 2 days(became lethargic, started swimming at water surface, rapid gill movements, leading to death by nighttime). These fish did not come into contact with the new clown killifish. I don't notice any white spots or external parasites on any of my fish, and my remaining fish seem active and healthy. I've honestly been blown away by how quickly this disease/parasite has gone through my fish. I'm quarantining any fish that seem lethargic or have rapid gill movements in a 2.5g bucket dosed with praziquantel and methylene blue, and have dosed my main tank with praziquantel after doing ~50% water change, but I'm not sure if it's helping yet. Any ideas about what could be happening? I've attached a photo showing 2 "lethargic" fish who appear to be in the early stages of the disease. Here's a video showing the difference between how they behave and how the other fish in the tank behave: https://imgur.com/alCiJcR. TLDR: Fish become lethargic, rapid gill movements and swim bladder issues appear within 10hrs of first seeming lethargic, death follows within 24hrs. No apparent external parasites. Did ~50% water change and treated tank with Praziquantel. Any ideas about what is causing this/how to treat? Here are my water parameters, tank has been setup and running for ~10years: Temp: 75-80F depending on time of day pH: 7-7.2 GH: 200ppm KH: 80ppm Ammonia, Nitrite: 0ppm Nitrate: 20-40ppm

Aquarium co op has an article about this. Relevant quote:

So I was watching Foo the Flowerhorn's latest video, and he added some type of leech (alboglossophinia lata) that eats snails to his tank to combat a snail infestation. Was wondering if anyone else has tried keeping these. How would they compare to, for example, loaches or assassin snails for snail control? Shrimp safe? Here's a paper I found studying these leeches. The meat of the paper is probably irrelevant to keeping them in aquaria. Relevant quotes:

I think dropsy is more of a symptom rather than a disease. Kind of like a cough; you can be coughing because you got an asthma attack, or because you have a cold. In one case, it is contagious, and in the other it is not. So whether or not dropsy is contagious or not depends on what was causing the dropsy. Here's a very graphic, but detailed video describing dropsy and some of its causes.

I had something similar happen too. If the bleeding is under the skin, this is probably septicemia which is either viral or bacterial in origin. If Maracyn 2 isn't working, you might want to try treating with a different antibiotic like Maracyn (Maracyn 2 and Maracyn target different types of bacteria). See the top post here. The guppy that got this died for me shortly after showing the streaking (~1 week). I treated it with Kanamycin (per instructions), salt ("level 1" dosing), and methylene blue (1 tsp/gallon). After hanging in there for a bit, she dropped 3 fry and died. I did not see symptoms in any of the other guppies (the ones that didn't die at least...) that came with her, so the infectivity seems low, but the causative agent might be different in your case.

Amano shrimp seem to enjoy destroying it as well. In my tank, I got this type of algae when I had high phosphate and low nitrate, but I have no idea how universal that is...

Just hatched my first batch of these! As mentioned, the separation rate is insanely good. Mine took a little longer to hatch than the ones I normally use though, closer to 30-36hrs than 24hrs.

I don't know enough about puffers to know for sure if it is gas bubble disease or not, but the large amount of small bubbles in your water after the water change suggests that your water is supersaturated with gasses. This can lead to something called gas bubble disease. I would recommend aerating your water change water before adding it to your tank. Although it is a little weird for this to occur if you are pouring in the water with a bucket...glad your puffer is OK though! Relevant quote: "Fins may be eroded with whitened fin tips and exophthalmia may occur with blood present in the anterior chamber of eye (...) Diagnosis is made by the observation of typical clinical signs and lesions. The presence of gas emboli in capillaries of the gills, fin rays, mouth and eyes are diagnostic."

Another option is methylene blue. Nitrites react with oxygenated blood to form methemoglobin, which stops the blood from absorbing more oxygen, suffocating the fish. Not sure what the effective dose is for fish, but the lethal concentration of methylene blue is quite high.

I was actually asking because I wanted to experiment with a blackwater tank! Very surprising to know that the Mopani wood provides tannins for so long!

I would expect GH/KH creep upwards if you are replacing evaporated water with tap water; over a long time period I would not be surprised to see GH go from 4 to 16 in this case. It is curious that the KH did not increase in the same manner. Only thing I can think of that would lower the KH is algae metabolism or calcium carbonate precipitating out of the water since you mentioned you have no live plants. Maybe someone else has experience with this? I wouldn't bother changing the GH/KH as long as it is stable and your livestock don't appear distressed. The only downside might be that if GH is very different in your tank compared to your LFS, new livestock might suffer osmotic shock without drip acclimation.

These look like the leeches that I find when I get blackworms. Pretty sure these give live birth; I cut them in half to feed to my fish so they don't propagate, and one time I cut one open, a bunch of little ones popped out from the middle...

Love susswassertang. Tons of surface area for biofilm/microorganisms to grow, little pockets for fry to hide, and grows in like..room light.