Tank upgraded from 10g to 20L - lost 2 fish

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Syprus21

Aquarium Advice Newbie
Joined
Jun 28, 2021
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My young son picked out glofish for our first adventure into aquariums. I did all the proper research and we've had 5 (purchased small) glofish tetra's in a 10gallon tank that was properly cycled before purchasing. Reading they like bigger schools and that 10gal is on the small side for 5, I decided to upgrade to a 20L and purchase 3 more glofish.

I did the move yesterday and I believe I did everything right. I am using the same HOB filter and a small sponge filter with air stone. I always check the water temps before adding and using a dechlorinator. I moved the gravel and decorations from the old tank and added some new gravel/decorations. I wiped/cleaned the new tank (with no chemicals) before starting.

This morning I've lost 2 of the original 5 (the 3 new seem fine). And 2 others of the original 5 are behaving a bit strange...1 seems to be near the surface more often than normal.

I can't for the life of me figure out what went wrong besides maybe just normal stress. I tested for Ammonia/nitrite and they are at 0. Water temp is the exact same as they had before (78F). The new fish aren't being aggressive at all, in fact one of the original seems to be bullying a little.

Any ideas? Water params seem great. Before anyone asks about PH, its the same tap i've always used for weekly water changes.

Thanks in advance.
 
Did you use a filter that's required for a 20g tank? So sorry about your fish! The reason it's swimming near the surface is due to lack of proper oxygenation so you should buy a sponge filter for 20g tanks. Glofish thrive in temperatures above 80 degrees fahrenheit, even though the Internet says they're cold-blooded in practice Glofish can't stand anything below 78 degrees fahrenheit; changing the fish tank water weekly is way too often for a tank as big as 20g since beneficial bacteria are trying to settle.

Moving to a bigger tank has taken a toll on your Glofish, with this advice I hope they get better!
 
Thanks for the reply. I have both a hang on back filter (suited for a 20gallon) that agitates the surface and an additional small sponge filter. These were both established in the 10gallon tank for a couple months. They've also been at 78 degrees just fine for that time period. The water temp in the new 20 gallon was exactly 78 when I moved them.

I was only doing weekly water changes in the 10gallon with already established bacteria, I have not done any in the new tank yet. The 2 fish died after the first night.

I'm still at a bit of a loss but thanks for the response
 
If ammonia and nitrite are zero, try a dose of your dechlorinator.

If your water system is doing a flush right now there could be way more chlorine in the tap than usual. I’ve lost fish twice just doing water changes during a water system flush :(

Now I just routinely double or triple dose with prime as a preventative because the water company doesn’t warn me when there will suddenly be way higher levels of chlorine.
 
Thanks...thats definitely possible I guess. The tank seems to have stabilized now, i lost 3 in total. Still no clue but a high amount of chlorine is possible and something I never considered. I did dose the standard measurement of prime but maybe I'll do double if i do large water changes in the future.
 
Yeah I didn’t either until I wiped out most of my tank during a routine water change. I checked with the water company after it happened and confirmed that there was a flush going on.

Then 2 years later I got caught again, one of the few times I didn’t double dose and I came back after a water change and a whole school of rummies was dead and all the other fish were at the top. Kicked myself and dosed another two doses of prime and all the fish (except the rummies, of course) went back to normal. Now I never dose less than 2x prime.

Check with your water company sometimes they’ll announce at least a range of time where they might be flushing.
 
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