Fish die within week of 100% water change

[Moby]

Hi there, I was hoping someone can give me some help.

I've had 4 betta fish over the past year or so. All of them were healthy and very interactive. However, each time I performed a full water change on my 2.5gallon tank, my fish would die within a week.

I made sure to gradually acclimate them into the new tank and added chlorine water treater, etc.

For my last fish, I was afraid to perform the 100% water change for this reason. I had him for 4 months and was performing maybe 1/5th water changes every few days. However last week the water was pretty dirty so I felt i had to do a 100% water change. Just found my fish dead this morning.

I am not sure what I am doing wrong and could use some help. Thanks.

[LittleBlueFishlets]

Can you describe your acclimation process in more detail? It sounds like something could be affecting them.

There are many ways to do a water change and acclimate (reintroduce) your fish back into the tank. Here is one variation:

1. Note the temperature of the water.
2. Using a plastic cup, scoop him, along with some of his water, into the cup.
3. Clean out the tank. Refill with water at the SAME temp. Be sure to add the correct amount of water conditioner.
4. Float his cup in the tank for about 15 min.
5. Add a SMALL amount of NEW water to the cup. (Several tablespoons, or about 1.5 ounces.)
6. Let his cup float for about 10 min.
7. If the cup starts to fill too much, remove a SMALL amount of water from the cup. Discard it.
8. Repeat steps 5-7, until about an hour has passed. (More time is always OK - there's no such thing as going too slowly.)
9. Gently release him into the tank.

Since you were doing only 20% water changes every few days, it's likely that ammonia and toxins were at high levels in the tank. Then, if you didn't acclimate (or rushed the acclimation) during the full water change, that the new water chemistry could have shocked his system. In unfiltered 2.5 gal tanks, the recommended water change schedule is one 100% and one 50% water change per week.

[Hadoken Kitty]

how often did you clean your tank?

[Sakura8]

Hi Moby. I'm sorry for your loss. That is very strange, as many of us perform 100% changes without any problems.

My guess however, is because you were only changing out 1/5 of the water every few days, the nitrogenous waste built up a great deal. Although this isn't healthy for a fish, they do adjust to such conditions. If you change these conditions suddenly and drastically like a 100% change, it can shock and stress them and send their immune system into a tailspin. Thus, they get sick. :(

My best advice for you is to start doing bigger water changes at a time. When you get a new fish, immediately get into the pattern of changing at least half of the water on a regular and frequent basis, depending on the size of your tank.

In general, if your tank is 1.5 gallons or under, I recommend at least a 50% change twice a week or more. 2 gallons or over, 50% change once a week or more. This reduces the buildup of ammonia, nitrite, and nitrate which can all harm a betta.

[Moby]

Thanks for the feedback. LittleBlueFishlets I followed a process nearly exactly as you described. I think the problem may have been that I should have done at least a 50% once a week