I have a 15 gallon tank in which I had 7 juvenile cardinal tetras and 12 juvenile pygmy corydoras for the last week (of 4 weeks QT).
I perform water changes daily or every other day with dechlor.
Fish have shown no sign whatsoever of illness - no odd behavior, no markings, eating properly, swimming actively etc. Observed them last night for a while and everyone was as fine as ever.
This morning I woke up and had lost 3 or 4 of the tetras and 5-6 cories. Dead, stuck to filter or on bottom of the tank. I immediately removed the bodies and performed a 50% water change with 5x dose of Prime. Some of the remaining fish look fine and some look distressed.
I tested the water which came out of the tank and it was 0 nitrites 0 ammonia.
I have come to 2 possible causes and wondering if this sounds what could have happened:
a) I put in a new heater last night because the old one wouldn't go below 80F even with it at the lowest setting. Is it possible the new heater has an electrical leak and shocked the fish? Temp is 78 so it didn't plummet or anything.
b) There is a small but real chance that last night I contaminated my tank with soap or even some hardcore scrubbing/cleaning powder while washing dishes and the cat's litter box and possibly moving right to tank activities. If this happened - is my bio filter likely also dead? I think to help with this possibility, when I get home from work before I leave for thanksgiving stuff I will replace the media with some from another tank's filter...
Thanks for any suggestions as to what could kill a large amount of apparently healthy fish overnight (8 hour span)
I perform water changes daily or every other day with dechlor.
Fish have shown no sign whatsoever of illness - no odd behavior, no markings, eating properly, swimming actively etc. Observed them last night for a while and everyone was as fine as ever.
This morning I woke up and had lost 3 or 4 of the tetras and 5-6 cories. Dead, stuck to filter or on bottom of the tank. I immediately removed the bodies and performed a 50% water change with 5x dose of Prime. Some of the remaining fish look fine and some look distressed.
I tested the water which came out of the tank and it was 0 nitrites 0 ammonia.
I have come to 2 possible causes and wondering if this sounds what could have happened:
a) I put in a new heater last night because the old one wouldn't go below 80F even with it at the lowest setting. Is it possible the new heater has an electrical leak and shocked the fish? Temp is 78 so it didn't plummet or anything.
b) There is a small but real chance that last night I contaminated my tank with soap or even some hardcore scrubbing/cleaning powder while washing dishes and the cat's litter box and possibly moving right to tank activities. If this happened - is my bio filter likely also dead? I think to help with this possibility, when I get home from work before I leave for thanksgiving stuff I will replace the media with some from another tank's filter...
Thanks for any suggestions as to what could kill a large amount of apparently healthy fish overnight (8 hour span)
