It seems I've got a problem with my 10 gallon tank (Previously stocked with 1 Male Half Moon & 5 Harlequin Rasboras). The tank has been up and running with no problems for around 9 months now. Water parameters are good (tested with API master liquid kit).
I lost a Rasbora lastnight, after noticing him breathing heavily, lose control and become very clumsy before passing on upside down. This morning, I woke up and found another Rasbora belly up at the bottom of the tank. When I got home from work today, I noticed another Rasbora starting to lose control, with the other 2 starting to breathe rapidly. After watching closely for awhile, he drifted into my Betta who was resting at the top of the tank. His response was brutal: biting and tearing an eye out. I quickly isolated the Rasbora, who ended up dying 20 minutes later.
I'm down to 2 now, and 1 is starting to float around upside down as I type. The Betta seems to be doing 'alright', being alert and eating with no problems, but I have noticed him resting sideways too often for comfort.
After doing some research, I believe my fish MAY have gill fluke. The rasboras gills do seem a bit swollen and red. I can't really tell with my betta due to his deep red coloring. I also believe I might know the POSSIBLE cause for this. A couple of weeks ago, I had a Mystery Snail die on me, presumably from old age. The problem was, when I went to pick her up to check on her, she basically fell to pieces out of the shell. I immediately started cleaning with a 50% water change and thorough vacuuming, but I have no doubt many parts were missed.
Any way, I'd just like to get some advice on whether my assumption here might be correct or not, and if it makes sense, the best way to treat it using fish meds (in the US). I did add some aquarium salt with a water change earlier. If anyone can help, I'd surely appreciate it. I don't want to run out and have to rely on petsmart staff...
EDIT: I'd also like to point out that I have seen my rasboras rubbing against tank decorations, presumably due to irritation.
What size is your tank? 10 Gallon Rectangular
What temperature is your tank? 78 F
Does your tank have a filter? Yes, Marineland Penguin 100b
Does your tank have an air stone or other type of aeration? Yes, usually on low flow, it is currently going full in an effort to help.
Is your tank heated? Yes, but haven't needed it in recent months.
What tank mates does your betta fish live with? 2 Harlequin Rasboras and dropping.
What type of food do you feed your betta fish? Hikari Betta Pellets, Frozen Bloodworms, Frozen Brine Shrimp
How often do you feed your betta fish? 2 small feedings per day. (2 pellets per, usually)
How often do you perform a water change? Weekly
What percentage of the water do you change when you perform a water change? 25-50%
What type of additives do you add to the water when you perform a water change? API Stress Coat +
Have you tested your water? If so, what are the following parameters?
Symptoms and Treatment
How has your betta fish's appearance changed? It hasn't, yet...
How has your betta fish's behavior changed? He is still very alert, but seems to be resting sideways often as of today.
When did you start noticing the symptoms? Yesterday, on a tankmate
Have you started treating your fish? If so, how? I added Aquarium Salt to the tank with a water change earlier.
Does your fish have any history of being ill? No
How old is your fish (approximately)? I bought him over 8 months ago, so I'd guess around a year?
Fish dying that fast often indicates something with water changed. The 78 is a bit low. Slowly going up to 85-ish is worthwhile. Most common would be ammonia or pH, but it sounds like both are in check. Dying animals often increase organic waste, and snails are carriers for disease. What did you check ammonia using? (I ask as some tests are not very accurate). Generally when a fish or animal dies and has time to decompose inside the tank, ammonia goes up a good bit. Also, nitrates sound a little low if the tank is fully cycled.
Is there any chance there was pH shock or a major temp flux? A minor pH or temp flux can wipe out an entire tank. Any chance the water wasn't dechlorinated on a recent change?
Are the fish scratching, is there change in locomotion, and has the slime coating changed? How about behavior?
I personally do not believe in the usage of salt and would advocate before doing anything as to treatment to diagnosing the problem. If there is no environmental cause determined, treating with a nitrofurazone cocktail is probably the best treatment as it is mild and wide spectrum.
Another possibility is the buildup of hydrogen sulfide which generally occurs when good bacteria dies, but dead organic matter can spike it as well.
The test results I was going by were 2 days old in my log. I decided to go for another round using my API Master Testing Kit. After the recent water change, I got a PH of 7.6 and at or very near 0 for Ammonia, Nitrites and Nitrates.
I don't see how a PH shock could come about, as my tank has remained 7.6 since I started it, and I get 7.6 out of the tap. Temp is possible, being the summer in southern AZ (There is no such thing as cold water out of the tap :P ) but my last water change before today's was just over a week ago, and I keep my place at 76-80 F at all times during the summer, with the aquarium heater set to 78 (I haven't seen it light up since April). As far as a dechlorination issue, that might be possible. I do remember last week noticing the tank level was getting low, so I mixed up some water to top it off, and I may have added it a bit too soon, as I noticed the water got a little cloudy afterwards. I've seen it happen before months ago, but it went away within an hour. This time it was there into the following day...
Yes, I have seen a few of the rasboras scratching/rubbing against decor when their symptoms started to get out of control. I am now down to 1 Rasbora btw. The survivor is just swimming in place angled upwards at the surface, breathing rapidly. The rasboras behavior has change in that they seem to be more oblivious to their surroundings, and they dont care about food. I see no visible changes in the fish, other than slightly swollen gill area. The Betta seems a tad lazier than usual, but as I said before I've noticed him on his side here and there as of today. It could be nothing on his end, but I'd rather be safe than sorry after seeing the others go so rapidly...
As for the salt, I was a bit desperate at the time, pulled out the box and read "Improves Gill Function".
Rubbing and scratching can indicate a few possible parasites...does the slime coating look any different and can you see any small white, brown, gold, or off-colored specks anywhere on the body? Is breathing different? Did you by chance get to observe what the gills of the deceased fish look like?
I did not make any close examinations of the deceased. I don't have the tools and my hands are pretty big so I didn't think I would get very far...
I just took a thorough look at the current survivor under good light. All seems to be normal, golden red and shiny. It's black markings are pronounced. I did notice a couple of spots that were particularly golden and shiny, one on it's head and another on the right side near the dorsal fin. I could be wrong, but it doesn't seem out of place to me as they've always exhibited these colors. The gills underneath appear pinkish red. Breathing is still rapid.
The fish did respond to the light by turning/moving away, and quickly darting away from my Betta afterwards, who seems to be taking advantage of the situation with smaller numbers...
The Rasboras are now gone... but my Betta seems to be doing just fine. Based on what Nick was saying, I do believe a sudden change to water chemistry wiped the little guys out. I'm still not sure how it happened, but what's done is done. :(
I'm glad I didn't just run out to the local petsmart and start dropping unnecessary meds in. I'll keep a close eye on the Betta, and lose the salt through future water changes. Thanks for the help.
Someone would have to confirm this but IIRC when organic matter such as a snail decays, it decreases dissolved oxygen levels...and if that is the case, the betta's ability to breath normal air would help it do better than the rasboras. The speed in which this happened combined with fish in good water without any display of illness makes environmental a strong possibility.