fish deaths

[Sharoane]

All right--that pesky green water has finally gone away and all my fish were doing wonderfully--that is, the three danios, the 2" pleco and four otos. Then an oto disappeared and another died, but I kept doing water changes and checking my levels and everything seemed fine and the other fish were fine. So. I bought four rummy-nose tetras, all no bigger than an inch long, and added them to my 30 gallon. They were doing great all day yesterday and last night, but when I got up this morning two of them were dead and the other two are swimming around with my danios. Nitrites were up to .25, the highest they've been in over a month, so I did a partial water change.

Any ideas why my fish would die? I've heard it's common for otos to die and I suspect my nitrates got a little high for them but I've been doing small daily water changes and the two I have left look very healthy. Is it common for new fish to die of stress? The other two rummynoses look great but so did their now-dead mates.

Help!

 

[tstenback]

water parameters are very important and when new fish are aded the parameters often change. these changes (increase in ammonia , nitraites, nitrates) can stress the current residents of the tank but can have a devastating effect on the new occupants as they are already stressed out from the move. Some will be fine and other sill just not be strong enough to recover. Keep up on the water changes and the levels should stabalize in a few days. Good Luck

 

[Sharoane]

Thanks...I guess my other question is how many fish at a time to add. When adding larger fish I try to go with two at most and with smaller fish no more than four. Again, for a 30 gallon that's not very heavily stocked.

I'm running two whisper filters of equal size right now and one of them looked like the bio bag had pretty much had it so I bought replacements. I rinsed the new bag in newly-drained tank water instead of the tap and only replaced one bag out of two--will that affect my tank in a big way?

 

[tstenback]

Those stocking levels are fine. just make sure you wait a couple of weeks between additions and if there is any disease outbreak then add this time to the 2 weeks.
That is the way to do the replacement of the bio bags when you have 2 filters. Should not have a great impact on the overall tank environment. I have even made smaller biobags and put 2 in each filter and only swap out 1 bag or 1/4 of the biomass at a time.

 

[Bangin]

Rummy nose are sensitive fish, and they require very clean water...ie. no ammonia/nitrite and low nitrates. The nitrites killed those two.

 

[Sharoane]

I checked levels before adding any new fish and pre-water change they were all fine. I've been doing small water changes every day because I had green water going on. Now it's slightly cloudy and instead of adding chemicals I decided to go ahead and take care of things the old fashioned way. I also change the water daily to keep the nitrates down.