What To Do About Harlequin Rasbora?

Back in May/June I added 8 Harlequin Rasbora to my 55 gallon tank. At the time there were 10 Cherry barbs and 1 rts living in the tank. Everything was good for the first week, but then slowly one by one they started dying. They all died overnight with no symptoms of being sick. Not sure if they had a parasite or if the rts ate them. They were very small no more than an inch or so and the last 2 to die I never found their bodies. I ended up losing 2 male cherry barbs as well. Cherry barbs had been in the tank for over a month before the new Harlequin's were introduced.

Currently the tank has the rts, 8 cherry barbs (3 that are over 4yrs old), and the 2 remaining Harlequins. One Harlequin is over 4 years old. The other is from May/June. Ideally I'd love to add more Harlequin Rasbora to make a full school of 10. However, every time I buy new ones I lose almost the entire stock I buy. It doesn't matter if I qt, acclimate for hours, I still lose most if not all of them. I don't know if the Petsmart I'm now using has a terrible Harlequin stock or if my Nitrates are simply too high for them and the older Harlequin is simply use to it? Please help! I love my Harlequin's but if I should rehome and find a different fish I'm willing to do that. I've never had issues with bringing in new Cherry Barbs (although I know they are generally a hardier fish), which is why I'm assuming whatever killed the Harlequins also killed the 2 small male Cherry Barbs.

I'm adding a pothos to help with Nitrates, as the tap has a consistant reading of 20.

 

What is your test readings for the tank (ammonia, nitrite, nitrate, pH, temperature, etc.)? What decorations and substrate do you have?

You said it doesn't matter if you quarantine, but from just your post alone it sounds like that's what may be wrong. I think you should quarantine longer, at least the 20 period that Pet Smart covers before you add the fish to your main tank. This will for sure eliminate the possibility of a parasite or illness.

I think you should've researched more about the Red Tail Shark before you got one:
"These fish can be hostile and are not recommended for community fish tanks with smaller tropical fish."
Red Tail Shark

When attempting to add a aggressive predator to a community tank, you should add them after adding the smaller fish so they can get "settled," meaning used to their surroundings and their new home. This means adding the smaller fish at least 24 hours before the predator. The predator will go through a bit of a shock trying to figure out his new home and may believe that the smaller fish are just a part of it. This MAY keep him from thinking the smaller fish as food, but if the fish is just too aggressive (like how it is with most Red Tailed Sharks) then he'll still attack them. When you add a smaller fish into a tank that already has a settled aggressive fish, they're completely defenseless. They'll be going through the shock and stress of transportation while acting very vulnerable to a unknown territory. This will trigger the bigger fish's instinct to take this opportunity and attack.

He very well could've ate your two fish. Now that he tasted what fish taste like I'm sure he was curious if your cherry barbs, known only to him as tank residents before, tastes the same.

 

Back in May/June I added 8 Harlequin Rasbora to my 55 gallon tank. At the time there were 10 Cherry barbs and 1 rts living in the tank. Everything was good for the first week, but then slowly one by one they started dying. They all died overnight with no symptoms of being sick. Not sure if they had a parasite or if the rts ate them. They were very small no more than an inch or so and the last 2 to die I never found their bodies. I ended up losing 2 male cherry barbs as well. Cherry barbs had been in the tank for over a month before the new Harlequin's were introduced.

Currently the tank has the rts, 8 cherry barbs (3 that are over 4yrs old), and the 2 remaining Harlequins. One Harlequin is over 4 years old. The other is from May/June. Ideally I'd love to add more Harlequin Rasbora to make a full school of 10. However, every time I buy new ones I lose almost the entire stock I buy. It doesn't matter if I qt, acclimate for hours, I still lose most if not all of them. I don't know if the Petsmart I'm now using has a terrible Harlequin stock or if my Nitrates are simply too high for them and the older Harlequin is simply use to it? Please help! I love my Harlequin's but if I should rehome and find a different fish I'm willing to do that. I've never had issues with bringing in new Cherry Barbs (although I know they are generally a hardier fish), which is why I'm assuming whatever killed the Harlequins also killed the 2 small male Cherry Barbs.

I'm adding a pothos to help with Nitrates, as the tap has a consistant reading of 20.

I have two harlequins I can send you if you are wanting to up their school. They have been with me in the same tank for several months now, fat and happy acting (I think they are two females). They can be delicate I lost the third one I had added (to try and bring up their school) with one of the others, but right now I had no plans to add more. They likely are weak stock I have had that issue with glass catfish knight now their school is five strong, it took me months to get even one to survive to getting into with the other four).

 

What is your test readings for the tank (ammonia, nitrite, nitrate, pH, temperature, etc.)? What decorations and substrate do you have?

You said it doesn't matter if you quarantine, but from just your post alone it sounds like that's what may be wrong. I think you should quarantine longer, at least the 20 period that Pet Smart covers before you add the fish to your main tank. This will for sure eliminate the possibility of a parasite or illness.

I think you should've researched more about the Red Tail Shark before you got one:
"These fish can be hostile and are not recommended for community fish tanks with smaller tropical fish."
Red Tail Shark

When attempting to add a aggressive predator to a community tank, you should add them after adding the smaller fish so they can get "settled," meaning used to their surroundings and their new home. This means adding the smaller fish at least 24 hours before the predator. The predator will go through a bit of a shock trying to figure out his new home and may believe that the smaller fish are just a part of it. This MAY keep him from thinking the smaller fish as food, but if the fish is just too aggressive (like how it is with most Red Tailed Sharks) then he'll still attack them. When you add a smaller fish into a tank that already has a settled aggressive fish, they're completely defenseless. They'll be going through the shock and stress of transportation while acting very vulnerable to a unknown territory. This will trigger the bigger fish's instinct to take this opportunity and attack.

He very well could've ate your two fish. Now that he tasted what fish taste like I'm sure he was curious if your cherry barbs, known only to him as tank residents before, tastes the same.

I have sand substrate with fake plants, and two small live anubias plants. pH is 8.2-8.4, temp 76 degrees, and tank ratings are as follows. Ammonia-0, Nitrite-0, Nitrate 20-30. Nitrates are a work in progress that's why I'm getting a pothos. This tank has been established for over 5 years, but we have recently moved and the water in the new house has higher nitrates in the tap.

You say for sure eliminate parasites or illness. That makes no sense. If they come in sick unless I treat them they will still be sick. I don't treat illnesses in qt unless they show signs of ich or illness. Hence, fish still dying if I qt them. Some are dying in qt before I can add them to the tank and yet others have died in the tank.

I'm well aware rts' can be agressive. I've owned one previously for many years in a community tank with no issues. My current rts is still a "baby" and is non-aggressive currently. I am unsure if it ate the smaller fish, just curious if it is possible. A few of the Harlequin would have been small enough to get sucked into the filter I think, but I don't want to rule out being eaten if it's a possibility. I monitor the tank frequently to watch for aggression and other issues. So far nothing outside of the Harlequin's dying.

The male Cherry Barbs I found dead were perfectly in tact. They did not vanish like the 2 Harlequin and the rts does not bother the Cherry Barbs or the other larger Harlequin. It's been at least 3 months since I've added any new fish and the rts still stays mainly in his "cave". He does not try to claim territory in several caves and has not been aggressive towards new fish. The 2 larger Harlequin's do not go near the bottom of the tank so they have never been harassed. The largest female Cherry Barb and rts swim together and share a smaller different cave than the rts' main "cave" so I am not currently worried about aggression in the rts, but I am always watching. It may not have been the smartest to get an rts when I'm still trying to stock schools, but he's still a baby and not aggressive. He was also introduced after I had Cherry Barbs and Harlequin already in the tank. I only had 2 Harleuqin at the time though which is why I'm trying to up the school. But the last two times I bought a few Harlequin home they didn't make it. The first ones never made it out of qt.

I have two harlequins I can send you if you are wanting to up their school. They have been with me in the same tank for several months now, fat and happy acting (I think they are two females). They can be delicate I lost the third one I had added (to try and bring up their school) with one of the others, but right now I had no plans to add more. They likely are weak stock I have had that issue with glass catfish knight now their school is five strong, it took me months to get even one to survive to getting into with the other four).

I'd love to up my school, but I'm unsure about getting fish through the mail. Especially if Harlequin's can be delicate. I do like the idea of fat and happy fish though lol. The Harlequin's at Petsmart are always so tiny! They go so fast though so I can't wait for them to get bigger at the store, I just have to hope they survive in qt/tank while being so small.

I was initally thinking weak stock, as the mystery snail I got from their died as well. But after waiting a few weeks I was unsure after only one survived in the second batch I bought. Ideally, I'd love to up my stock, but want to make sure they can/will survive if I decide to get more. It looks like the Petsmart is going through a make over in their fish department, so I'm hopeful this means the water quality will be better and the fish will be healthier.

 

I'd love to up my school, but I'm unsure about getting fish through the mail. Especially if Harlequin's can be delicate. I do like the idea of fat and happy fish though lol. The Harlequin's at Petsmart are always so tiny! They go so fast though so I can't wait for them to get bigger at the store, I just have to hope they survive in qt/tank while being so small.

I was initally thinking weak stock, as the mystery snail I got from their died as well. But after waiting a few weeks I was unsure after only one survived in the second batch I bought. Ideally, I'd love to up my stock, but want to make sure they can/will survive if I decide to get more. It looks like the Petsmart is going through a make over in their fish department, so I'm hopeful this means the water quality will be better and the fish will be healthier.

I can always see them in the tank and they don't get bothered by the other fish, I just don't have plans to try and add more to their school. They are fun to watch especially on brine shrimp/blood worm day.
You can try giving them garlic juiced foods to help boost their immune system along with whatever other QT process you have going on.
The good thing is you aren't terribly far away from me so it wouldn't be as long a trip as some fish I have sent out lol. (I had a pair of angels take four days to reach their new owner but arrived in fine shape).

 

Provided with further details I also do not believe that the RTS has any fault. The only thing I can think of is probably the quality of the fish from the store. PH of 8.2 sounds a bit too high for me as I heard that these fish are usually kept in planted aquascapes, but I heard that pH mostly matters when breeding so I would assume they'll be able to adapt...

 

Provided with further details I also do not believe that the RTS has any fault. The only thing I can think of is probably the quality of the fish from the store. PH of 8.2 sounds a bit too high for me as I heard that these fish are usually kept in planted aquascapes, but I heard that pH mostly matters when breeding so I would assume they'll be able to adapt...

I was also concerned about pH at first but was told a stable pH is better than one that fluctuates too much. Hoping they will adapt if that was the issue.

 

Wonder what the ph is at the store you get them. I have 13, amd I these guys have been through ****, tail fins bit completely off and such, and not one has died. Mine have survived in ph of 5.5 to 7.6 . Idk any higher.
This guy, I thought I was gunna lose him, 3 days later, you coukdnt hardly tell a difference. Between him n the others. He was litterally bleeding out, had something inside, that big spot was protruding, then the next day, I dropped my ph from 7.2 ish down to below 6 and he wasn't fazed.

They only breed in acidic water, so id bet they don't fare well in higher alkalI water

 

Wonder what the ph is at the store you get them. I have 13, amd I these guys have been through , tail fins bit completely off and such, and not one has died. Mine have survived in ph of 5.5 to 7.6 . Idk any higher.
This guy, I thought I was gunna lose him, 3 days later, you coukdnt hardly tell a difference. Between him n the others. He was litterally bleeding out, had something inside, that big spot was protruding, then the next day, I dropped my ph from 7.2 ish down to below 6 and he wasn't fazed.

They only breed in acidic water, so id bet they don't fare well in higher alkalI water
View attachment 358220

They can adjust as long as you aren't being too harsh, the two I have adjusted from store's 7.0ph to my 7.6ph without issue. Not as large a difference I know, but they can adapt as long as you are careful.

 

They can adjust as long as you aren't being too harsh, the two I have adjusted from store's 7.0ph to my 7.6ph without issue. Not as large a difference I know, but they can adapt as long as you are careful.

True, but if the op store is 7 or lowerbph and theirs is in the 8s like said, that may be a part or all the issue id imagine. When my ph dropped, I lost my guppies 1 by one, no more than 2 a day and at different times.

I think itd be a smart idea atleast

 

True, but if the op store is 7 or lowerbph and theirs is in the 8s like said, that may be a part or all the issue id imagine. When my ph dropped, I lost my guppies 1 by one, no more than 2 a day and at different times.

I think itd be a smart idea atleast

I haven't tested pH in a few months since it's been stable but I'll retest it and see where it is at. What is the best/safest way to lower pH? Is that something I should consider or will it harm the fish currently in the tank?

 

You would have to lower it very slow with that high of a ph, but it may still swing of your method fails and potentially kill your fish from ph shock. I think it would be easier to keep it stable instead of trying to change it.