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Discussion Starter · #1 ·
Good evening,

I have been having problems with my last two water changes where a fish died the day after the water change. I have been doing the water changes the same way for the last 6+ months on this tank and this is the first time I have lost fish. Any possible causes/suggestions would be greatly appreciated.

One thing I thought of was that I have been using the same bottle of Prime for quite a while. I am not sure if there is an expiry on it. Might that be a possible cause?

Tank size: 75 gallon
Substrate: pool filter sand
# of fish when this first started: 6 (~ 3-4" each)
Canister Filters: Sunsun 404B x 2 (rated at 525 GPH each)
Water Change: 25% every week or two. 25% of the water is removed. The temperature in the tank is measured using NIST certified thermometer. 13mL of Prime conditioner added to the tank. The same thermometer moved to source water and temperature adjusted until it is the same as fish tank. Python system used to pump tap water into the fish tank.

Thanks,
Rob
 

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What are your test results for pH, ammonia, nitrite and nitrate?

Some water authorities increase chemical treatment in the spring or periodically for a shock of chlorine, chloramine, etc.

Check and see if they did this recently. The extra chemicals can overwhelm the Prime.
 

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DJRansome said:
Some water authorities increase chemical treatment in the spring or periodically for a shock of chlorine, chloramine, etc.
+1. I would always use at least double the recommended dose of Prime for those times your water company does work in your area and they flush the lines with the disinfectant afterward. You can use triple the dose, or more, without any adverse effect on your fish.

Have you noticed your fish displaying any odd behavior in any way right after the water changes?

Prime has a "practically unlimited shelf-life".
 

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Discussion Starter · #4 ·
Thanks for the quick feedback.

I will double-check the water parameters before and after this next change. However, every since I completed the fishless cycling back in December, I have never had ammonia or nitrites. Nitrates are consistently high, but this has always been the case in this tank and in the small tanks that I have had over the year with no deleterious effects on any fish. It could be a number of factors that have coincided now where the high nitrates are making a difference so I really do appreciate all brainstorming efforts.

On the Prime situation, I do believe I am adding extra. The amount of Prime to treat 75 gallons (per the bottle) is 12.5 mL, which is what I add prior to adding the water. However, I am only change 25% of the water. In addition, the amount on water held by the tank is less than 75 gallons taking into account sand and rocks, etc. So I figure I am using 4x+ the recommend Prime. Honestly, I was concerned if I could be using too much Prime.

Thanks,
Rob
 

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I would definitely increase your water changes to weekly or more often and gradually increase up to 50% weekly minimum.

But DO check with the water authority. If it happened, then you will know why. If it didn't you can look further.

Also if it happened you know to be alert to municipal activities and you can avoid water changes entirely during those times.

If you think it is not the water, then next concern is illness. What are the symptoms of the fish that died?
 

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Indywar2 said:
On the Prime situation, I do believe I am adding extra. The amount of Prime to treat 75 gallons (per the bottle) is 12.5 mL, which is what I add prior to adding the water. However, I am only change 25% of the water. In addition, the amount on water held by the tank is less than 75 gallons taking into account sand and rocks, etc. So I figure I am using 4x+ the recommend Prime. Honestly, I was concerned if I could be using too much Prime.
If you're adding the Prime directly to the new 25% water before the water goes in the tank then this is correct. But if you're adding the Prime to your aquarium then you are supposed to use the amount based on the tank's entire water volume since Prime also binds to the nitrite, nitrate, and ammonia molecules in the water.
 

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Discussion Starter · #7 ·
Thanks again to both of you for the good suggestions. I have contacted the water dept. I will plan to increase the amount/percent of the water changes. I always thought more than 25% could mess up the aerobic/anaerobic bacteria biofilms that convert the ammonia and nitrites. It sounds like up to 50% is still okay to avoid that?

Thanks again for the help,
Rob
 

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Aerobic bacteria are not much of a feature of freshwater tanks as they are highly oxygenated. The beneficial bacteria live on the filter media and other surfaces, not in the water column. Don't go from 25% to 75% and don't do 75% if the town has shocked your water system...but 75% and really any amount is safe as long as you match parameters.
 

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DJRansome said:
Aerobic bacteria are not much of a feature of freshwater tanks as they are highly oxygenated. The beneficial bacteria live on the filter media and other surfaces, not in the water column. Don't go from 25% to 75% and don't do 75% if the town has shocked your water system...but 75% and really any amount is safe as long as you match parameters.
Just a little typo. He meant anaerrobic, I think. Anyways, just wanted to add that after heavy rains, they often boost chlorine/chloramine. Some fish within the same species are genetically more vulnerable to chemicals, just like some humans have peanut allergies. When I was much younger, I had a 10 gallon tank, that I begged my parents to get. On the initial fill, instead of using dechlorinator, my dad used water clarifier. This killed all but two zebra danios, who lived for many months. Over the course of the period, we added new fish periodically, and the new fish died. After some dead fish, I decided to take the aquarium matters entirely into my hands, and that's how I got really hooked onto the hobby. I tested the water, found chloramine, dechlorinated it, waited a few weeks for BB to form, and then added new fish. They survived. I think those danios were just tough cookies.
 

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You are right about anaerobic...and I typed anaerobic as well. Auto correct.

It's like every time I type elongatus the auto correct changes it to elongates. I fix them but I'm sure I miss some.
 
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