How Many Water Changes In A Row W/o Losing Biofilter?

blissfulbunny

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HI fish peeps:

How many water changes can I do in a row without losing my bio filter?

AC 70 filter with one regular sponge and two bags of media.

Very mature, 20 gallon long, freshwater, community tank. 6 Corys, 5 Tetras, 5 Amano Shrimp, 4 male guppies, a few non-pest snails. Lots and lots of foliage. No recent changes.

I do 70% water changes every three weeks with no problems. I don't have a lot of livestock, and a lot of foliage. But it has to be three weeks.

The usual story. Waited a bit longer than usual for a water change. Probably a little overfeeding. Not much, I skip a day once or twice per week. I didn't see any dying plants or detritus on the gravel. All fish accounted for.

YESTERDAY
Tested at 40ppm for nitrates (ammonia & nitrites always zero). The fish did appear a little stressed.

#1 70% water change. Did the usual thorough vacuuming of gravel. Did not test again. "Surely 70% will take care of it." Not.

TODAY
Woke up this am, very noticeable bacteria bloom (cloudy white). 80ppm for nitrates!
#2 70% water change about four hours ago (at 6:40p Pacific). No vacuuming of gravel. Jest tested, back to 40ppm nitrates. Cloudiness is much less. The fish no longer look stressed. They have that "water change, all new water, tear around with glee" look to them.

QUESTION: Should I go for #3, or wait for the bio filter to catch back up?
 

david1978

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Your bacteria is primarily in your filter not your water so in theory you could do 100 75% water changes in a row with no change to your beneficial bacteria .
 

Skavatar

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blissfulbunny said:
Hi, thanks for the reply. Wouldn't this starve the bacteria within a few changes?
nope, b/c fish are constantly producing ammonia.

the bacteria bloom could have been caused by the excess detritus being stirred up during gravel vac or when refilling.
 

david1978

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Even with no ammonia it takes around a week for it to go dormant and a month till it starts dying off. So as skavatar said no worries on that.
 

kallililly1973

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Could you add some house plants to your filter to try to help with the nitrates? Pothos are suppose to be good for getting them stable. I’m sure it wouldn’t take care of em overnight but it should eventually help out. also did you test your tap for nitrates? Will the potato hanging in the tank also take care of high nitrates through time? Just a thought.
 
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blissfulbunny

blissfulbunny

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kallililly1973 said:
Could you add some house plants to your filter to try to help with the nitrates? Pothos are suppose to be good for getting them stable. I’m sure it wouldn’t take care of em overnight but it should eventually help out. also did you test your tap for nitrates? Will the potato hanging in the tank also take care of high nitrates through time? Just a thought.
Hi. I usually don't have a problem at all with nitrates (etc.). I test regularly, and I always get 0 ammonia, 0 nitrites, no matter what. And I seldom test higher than 5-10 nitrates. So as long as I keep up water changes enough to avoid nitrate build up, I am fine.

In this case, I think I slipped a little into overfeeding, plus I have sand so when I vacuum, sometimes some organics get buried just slightly (the Corys shift the sand around and over on itself) that get stirred up. So I had a perfect storm of bacteria bloom with so much organics/bacteria food in the tank. It just takes some work (water changes) to get the excess bacteria out of the tank.

I did look up nitrates in Las Vegas water once, and there were definitely some, but not an excessive amount.
 
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blissfulbunny

blissfulbunny

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FOLLOW UP:

Day one:
Fish look stressed.
Tested at 40ppm for nitrates
Water change #1: 70% water change

Day two:
Very cloudy water
Tested at 80ppm nitrates
Water change #2: 70% water change
Water clearing

Day three (today):
Water is clear
Tested at 10ppm

FYI, here's an interesting article in The Spruce about rapid reduction of nitrates: . Maybe I'll try next time.

Thanks again, fish peeps.
 

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