Problem with fish dying...

[jRaskell]

History. This is my mothers tank. Given to her a month ago, 30 gallon tank, initially plopped 4 neon tetras in it.

2 week later, she gets 4 angelfish and an algae eater.
5 days later, all the angelfish and algae eater die within a period of 24 hours. It was at this point that I came in to do some investigation. I knew nothing about keeping aquariums. After some research I learn about cycling, ammonia and nitrite buildups, and water changes. I grab some test kits, her ammonia readings were very high.

So we wait to let the tank cycle, doing 10% water changes every week. I have her test the water every week. Yesterday she tests and zero ammonia, zero nitrites (just over 2 weeks later). Nitrates are a bit high at 40ppm, but still within what I've read is livable specs. We do another 10% water change today (letting the 3 gallons of water set overnight, about 15 hours total).

We go out and buy a couple golden algae eaters (much smaller than the first algae eater she bought, which would have been 18" long at adult). Both golden algae eaters are dead within 3 hours.

I test again, 40ppm nitrates, 0 ammonia, and 0 nitrites. pH is low at 6.2 (or could it be even lower? 6.2 was bottom of scale) I'm not sure what's killing the fish. Is it the pH? Do I need to get something to bring the pH up around 7.0? I'm a bit at a loss here, and if I can't help my mother keep her fish alive, I'm going to be reluctant to get my own tank.

 

[Ryoken]

Very odd, need more info... sounds like you have something bad (poisonous) in the tank or the pH is *really* low.

I assume the original 4 neons are dead?

What kind of chemicals have you added to the water? (stuff like dechlorinator, fertilizer for plants ect.)

What do you have for decorations in the tank? Any gravel?

If you used tap water to fill the tank:
What is the pH of your tap water? Any nitrates in the tap water?

If you didn't use tap, what did you use?

What temperature is the tank water?

I've never had the pH of my water off the scale before, but I think my test kit reads down to 4.5. You'll need a test with a bigger range to find out your actual pH...

 

[Lukara]

How did you acclimate the new fish?

When I get new fish I open the bag and let it float in a bucket of water (which is the same temperature of the aquarium, maybe a wee bit warmer) to keep the bag's water from getting cold, I do this for an hour.

During this hour, I take 1/4 cup fulls of the actual water in the quarantine tank and pour that water into the bag every 5-10 mins for a total of an hour. To be on the safe side I test the bag water's PH and temp at the end of the hour to ensure that it is the same as the aquarium's water. Then I net the fish out of the bag and put him into my quarantine tank.

If you didn't acclimate your fish properly, it could be that the bag water's PH was significantly higher than your aquarium water (6.2 is quite acid) and this is enough stress to kill any fish. It is my understanding that changes in PH shouldn't be more than +/-.2 per hour. Also a significant difference in temperature is enough to stress a fish to death.

Hope this helps.

Editted: Originally I wrote that the PH shouldn't change more than +/- 2 per hour. This was a typing mistake, I changed it to read +/- .2 per hour.

 

[jRaskell]

The original neons are still all alive and apparently well.

Acclimating...

I sat the bag in the tank. Opened it 15 minutes later and mixed in some tank water (probably about half as much as was already in the bag) and let it sit for another 15 minutes, then emptied them into the tank completely. Unfortunately I never tested the original water in the bag to get a comparison. Perhaps that was the problem.

We are using a little bit of stress coat, but only about half what the instructions say to use since we are letting the water sit overnight before doing the water change.

 

[Lukara]

I've always acclimated new fish this way and never had any deaths. You might want to try what I said for any future purchases. The idea is to make slow changes to the bag water over a period of time so that you don't shock/stress the fish. The more there are differences in your tank's water and the bag water, the longer the acclimating should be. Slow 1/4 cups of water every 5-10 minutes for X hours (depending on water differences) while the bag is opened and floating in the aquarium or bucket.

 

[Ryoken]

Ahh, well if the neons are still alive and kicking, then pH shock killing the new fish sounds pretty likely.

Neons do well with a low pH (neons can go really low) but even if you acclamate any new fish slowly, most are not gonna last if your pH is 4 or 5. You need to find out what your pH really is and why it's so low before you get any more fish. It could just be that your source water is really soft/acid, if so, there are a bunch of ways to raise your pH/hardness. I wouldn't any of the pH adjusting chemicals to do it though, and certainly not before you know your hardness (GH and KH.)