Tropical Fish Keeping - Aquarium fish care and resources

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Deceeve 08-23-2010 10:49 AM

New aquarium, all fish dead
Thank you in advance for any insight into what may have happened.

I started a small 10 gallon freshwater aquarium 4 weeks ago. I washed everything per the instructions, and let it filter without fish for a full week. I started with (sorry for lack of real species names) an orange Molly and a Glass Fish(the ones you can see through). For two weeks they did just fine, eating normally, swimming normally, etc. The water did get a little cloudy, I read about it and believe it was bacterial bloom, so I followed the instructions for water care for that.

Now, last Friday I added 1 more orange Molly, 1 more glass fish, and a cory catfish, this was going to complete my fish in this tank. I let the fish soak in the tank for 30 minutes, dumped 80% of the pet shop water, and then dropped the fish in. Within 24 hours, the new Molly was dead. Within 48 hours, all fish in the tank were dead, including the two originals. The weird thing is, this morning I looked in the tank again for some reason and found 5 baby mollies swimming around.

The temp was a steady 78 degrees. I did not take ph reading for the tank. Nothing changed in feeding habits, etc.

Any ideas to what could have happened?

Byron 08-23-2010 11:12 AM

Welcome to Tropical Fish Keeping forum. Sorry your first post has to be a problem, but we're all here to help.

I suspect that rather than one specific issue it may well have been a combination. The tank was not cycled when fish went in, new fish were added too soon, store water was added to the tank...any one or all of these are trouble.

First, cycling a new tank. I don't know where stores dream up this idea that running an tank for a week without fish somehow cycles it. It won't. There has to be a source of ammonia, usually from the first fish, and then bacteria have to appear (they do naturally but it takes time) and the cycle has to become established, which can take 2 to 8 weeks normally. Here's a good article on cycling from the "sticky" at the head of this section, have a read for background information on cycling:

I'm surprised the first molly in the tank lasted so long; mollies are highly susceptible to ammonia poisoning. Even if ammonia (and then nitrite) doesn't kill the fish outright, it severely weakens them internally and they may struggle on for weeks before dying.

Second issue was introducing new fish. Never add water from the bag to an aquarium. The bag water contains ammonia from the fish in the bag, and you don't need more of that; it may also contain pathogens, parasites, disease--who knows what may be living in the store tanks, even if the fish seem OK, they can still carry things with them. There are two similar methods of introducing new fish:

1. Open the bag, carefully remove some of the water if there is a lot, then float the bag in the aquarium for 20 minutes to equalize temperature; I do this by placing the bag at one corner and bending the top over the edge so the bag stays upright and the waters don't mix. After about 20 minutes add some of the aquarium water to the bag; I use a cup. Drape the bag over the frame again and leave for 15-20 minutes. Repeat with another cup of water. If the fish are particularly sensitive, I may do this 3 or 4 times. Then, with a small net, net the fish out of the bag and into the aquarium. Discard the bag of water.

2. Similar to above, float the bag to equalize the temp. carefully pour the fish and bag water into a small pail (only for aquarium use obviously), and run a drip line from the aquarium to slowly drip aquarium water into the bag. A piece of airline tubing works for this. When the water in the pail has doubled, which should take several minutes, net the fish out and into the aquarium.

Back to the present issue: as you have fry, I would leave the tank "as is" and let it cycle. Get yourself a test kit, API make a good one, liquid (not strips), a combo that includes ammonia, nitrite, nitrate and pH is sufficient. The growing fry (if they survive) will cycle the tank very slowly, but it will work.


Deceeve 08-23-2010 11:31 AM

Thank you very much Byron. I am very disappointed that following the directions in the aquarium could result in this. I appreciate the information and will read that sticky asap. Have a great day!

aunt kymmie 08-23-2010 11:54 AM

Welcome to the TFK, Deceeve. I'll be pulling for your fry and hope they survive the cycle.

kitten_penang 08-23-2010 04:29 PM

smaller fish seem to fair better in tanks's weird 0.0 sorry your fish dies though.

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