Cardinal Tetras Sucked To Filter Tube

[wpascarelli]

Recently started up a 55 gallon community tank with some dwarf rainbowfish and corys, and today I received a shipment of some Cardinal tetras, around .75" - 1" size, to go along with 2 regular neon tetras that were given to me that were already in the tank with the other fish. The cardinals had lost a lot of color during shipping but seemed to be doing fine when I put them in the tank. I watched them for a little while and then left for a couple hours. Came back a little later and found 2 of the cardinals stuck to the filter pipe. One was already dead, and one was not in good shape. I immediately turned off the filter and removed the dead one and put the bad condition one in a quarantine tank.
Is there anything else I can do to help this fish?
My filter is a HOB Fluval C4. I had these other fish in the tank, including the 2 neons, for a few weeks without any issue with the filter, do you think this was due to them being weak from shipping and normally this would not happen? Or should I modify the filter pipe somehow to prevent this from happening in the future?


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[BettaBettas]

(I would get some more neon tetras as they travel more in groups)
 
Also I wouldn't change the filter tube, but did u acclimate the fish?

 

[wpascarelli]

Well the 2 neons that were given to me should school with the school of cardinal tetras. This is also not related to the Cardinal tetras being sucked against the filter tube.
I floated the bag for ~30min before releasing them.


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[Munroco]

It could well have been the fact that they were too weak from shipping to avoid being sucked in. Is that a particularly powerful filter? Putting mesh over the intakes would stop fish being sucked up.

 

[Byron]

I would tend to think the acclimation was more to blame, or the fish may have been injured and weak.  If wild caught, you probably would not believe what an ordeal these little fish go through to get to the store--it is frankly amazing any survive.  With sensitive fish like characins (tetras, pencilfish, hatchetfish) a longer acclimation with mixing of the water is advisable.  The difference in GH, KH, pH and TDS can be traumatic for fish.  One of us can explain the acclimation procedure if asked.
 
As to the filter, if it is strong enough to pull fish in, using screen will not help, as the fish will still be pulled into/against the intake.  But in most cases this is less likely the issue, and the fish are more likely to be weakened by something.
 
As to cardinals and neons shoaling, yes, they will.  The three species in Parachierodon are closely related (aside from the obvious external similarities), and they will shoal together.  Given that you had the two neons, and assuming you wanted cardinals, acquiring a group of the latter is fine.  The neons will be relatively settled.  Cardinals and the green or false neon are actually much more closely related (in terms of DNA) than either is to the true neon, but they are still close relatives.
 
Byron.

 

[DoubleDutch]

Agree with Byron about the acclimation being culprit. Healthy fish will seldom be sucked to / in a filter.

Are you sure about schooling Byron. In mybexperience the schoolingvehaviour of cardinals is totally different than neons. Cardinals are tight shoalers cruising the tank, neons creating small groups (when ar ease).

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[Byron]

Agree with Byron about the acclimation being culprit. Healthy fish will seldom be sucked to / in a filter.

Are you sure about schooling Byron. In mybexperience the schoolingvehaviour of cardinals is totally different than neons. Cardinals are tight shoalers cruising the tank, neons creating small groups (when ar ease).

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Difficult to answer with any certainty, and it has been many years since I have kept neon tetras.  I have cardinals and the false/green neon, and together presently, and they are always together.
 
I have found with characins that if the shoal is reduced, say due to old age, with just one or two left, and when I am unable to acquire more (or decide to move on to other species anyway), the survivors sometimes tend to "attach" themselves to another species, though there is no true shoaling behaviour as one sees within a species.  But I assume this helps to keep the survivors less stressed.  Sometimes they remain isolated.  I have two Hyphessobrycon loretoensis in my 40g that are the last of a group of 10 that I acquired some six years ago, and these two never interact but remain separated.  A couple months back there were four in the survivors, and they also tended to remain isolated.  This is why I tend to suggest that lone survivors be kept where they are, if further numbers for the species are not feasible.
 
I have not found cardinals particularly tight shoaling, generally speaking.  My experience has been with wild caught fish (commercially raised cardinals are available, but I have avoided them).  In their habitat, observations apparently show that when they are "exposed" in a more open environment they will remain together in hundreds.  But when they are in their more preferred habitat, one with lots of branches, they break up into small groups of 5-6.  I doubt my tanks have been  large enough to replicate things like this, and being well planted with lots of wood the cardinals have spread out.  The P. simulans are less inclined to do this, generally.
 
Byron.