Fish wipe on Tues night/weds... :(

Discussion in 'Fish' started by sanj, 31 Jul 2008.

  1. sanj

    sanj Member

    Coventry, UK
    Came home yesterday to find 11 of the 27 fish in my rio 400 dead.

    10 of these were the entire school of denisoni barbs. :(
    1 was a kutubu rainbow.
    The other fish that survived were rainbows, a RTBS and a SAE.

    I am suspecting that it was oxygen depletion although not 100% sure.

    I have taken co2 off for about a couple of weeks although there is still considerable plant mass (im in the process of setting up a larger tank). So i think CO2 build up is still possible in the night, plus the higher temps over the last week or so (reading 27c).
    I had conducted a 40-50% change of water and had also added some melafix and pimafix as one of the rainbows seem to have a small infection on the mouth(nothing unusual or major, common in many rainbows). However im thinking that maybe these could lower the O2 level?

    I had this situation about 2 years ago when i lost my entire stock. Think now I will add an aeration pump to the new aquarium that will come on at night time.

    checked water parameters, seemed ok although nitrates around 30ppm, this could have been from the water tap water which sometimes has this level of nitrates. Have not dosed since removing the co2.

    I am guessing that maybe the medication may have tipped the balance, im not sure though, plus doing a water change one might think that that would help aleviate any oxgen depletion.

    However the fish lost wad almost all just denisoni barbs and not the others.

    Very sad, any other ideas?
  2. LondonDragon

    LondonDragon Administrator Staff Member

    I had this happen when I first started with CO2, I unplugged my airstone to do something in the tank and forgot to put it back on, two days later most of my fish were dead, have since been running two airstones during the night, just incase one fails, I seem to have two of everything in the tank nowadays lol. But its strange if you have been running like that for a while.
  3. a1Matt

    a1Matt Member

    I am not an expert, but your theory that the O2 levels were pushed too low due to the meds sounds right. I guess the barbs were the most sensitive fish in the tank at that time. I would also guess that your O2 must have been borderline before the meds.

    My commiserations to you on losing the fish.
  4. GreenNeedle

    GreenNeedle Member

    Lincoln UK
    Melafix and Pimafix are organic meds and will not deplete oxygen. They don't require 'removing' with carbon as they are biodegradable.

    Temp of 27ºC is not overly hot either.

    Are you running pressurised or DIY? Most of us have never run an airstone, and many of us have at some stage run CO2 24/7 with no problems. I was running 24/7 last year when the water temp got up to 32ºC with no problems at all.

    My guess is a disease of some sort rather than CO2. If it was oxygen depletion they would've all died not just some as would a CO2 overdose.

    Nitrates of 30ppm is nothing to worry about either.

    IMO parsite/infection/disease of some sort.

  5. sanj

    sanj Member

    Coventry, UK
    The only reason i wasnt thinking of disease is because it happened just over night, there were no warning signs earlier, fish were active, eating normally.
    The dead fish didnt show anything external that was obvious.

    The denisoni barbs are known to be high o2 demanding plus prefering lower temps around 24(on average) which could explain why all of them and only one of the rainbows died.

    The co2 i used before was a 2kg pressurised cylinder injecting into a JBL bubble diffuser.

    Had this aquarium set up since end March, no problems until yesterday... oh actually one of the denisonis did have dropsey, but seemed to recover but that was a month ago and it showed symptooms for a bout a month beofre that before it recovered.

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