Weird nitrate results with seeded filter?

endlercollector
  • #1
As part of my daughter's science fair project, phase 2 consisted of putting fabric bits pulled from one of my filters into a nylon sack in a Whisper i3. For substrate, she used gravel from a guppy tank. These all went in a 2-gallon with her Betta Lazo to see if she could get an instant cycle. She is using no carbon, zeolite, or other filter material, just the sack with the fabric bits. This is what's going on:

end of week 1: ammonia 0 ppm, nitrite 0 ppm, nitrate 40 ppm; 75% water change

end of week 2: ammonia 0 ppm, nitrite 0 ppm, nitrate 20 ppm; 75% water change

end of week 3: ammonia 0 ppm, nitrite 0 ppm, nitrate 160 ppm (???); 75% water change.

One thing I did notice: the temperature has dropped about 30 degrees in the last couple of weeks, and the heat has been going on in the house. The water does seem to be evaporating much more quickly, and my daughter hasn't been topping off the tank, so it's been at times 20% lower than it ought to. Would that concentrate the nitrate? Wouldn't there be some loss of the nitrate as well due to evaporation?

I'm not letting her move on to Phase 3 (putting Lazo in the Walstad-inspired tank I'm helping her set up) until she gets consistent readings. I'm so mean... The beatings, ahem, I mean, the water changes will continue!
 
LyndaB
  • #2
I'm no rocket scientist but I have to think the evaporation had something to do with it.

I'm confused as to whether you just tossed that sack into the tank or if there's a filter involved?

Maybe the sack is not allowing the water to flow through and so the beneficial bacteria is not populating there as it should be. Or, maybe you didn't get enough fabric.
 
jileha
  • #3
The only thing that evaporates is H20. That's why it's a good idea to use distilled water for refills. If you keep adding tap water with refills, whatever minerals it might contain will end up accumulating in the long run. In my first days as fish keeper I did just that, very few wc because all parameters were perfect, just topping off with tap water. And then my fish started dying. Took me a while to figure out why. This was before the days of the internet with all its readily available wisdom.

Otherwise, I had a very lousy chemistry teacher in high school, so I guess the nitrates would concentrate more in less water. 160 ppm seems a bit big jump from 20 the week before, though.

Do you have any decaying plant matter in the tank?


Maybe the sack is not allowing the water to flow through and so the beneficial bacteria is not populating there as it should be. Or, maybe you didn't get enough fabric.

Good thinking, but wouldn't that in particular affect the ammonia and nitrite readings? That there's only nitrate should indicate that there are enough beneficial bacteria. There just seem to be too much waste products in the cycle.
 
Mamajin
  • #4
I agree with Lynda.

The water evaporates, but the stuff in it does not. The more water you lose due to evaporation, the more concentrated those things become until eventually the water is too toxic for the fish. Top offs are extremely important to prevent high concentrations of toxic things in the water column.

I didn't learn about this until a few months ago as it was addressed in a Q&A in one of the Tropical Fish magazine issues.
 
EricV
  • #5
That does seem like a quick jump. However as has been stated nothing but h2o evaporates out of your tank so things like nitrates, salts, fertilizers, and other impurities will stay behind and become more concentrated over time unless you are topping off with with distilled water. A TDS meter is probably the easiest way to keep an eye on this (and at $10 it isn't much more expensive than the other random tests we have).

On the plus side the nitrate production shows that the cycle is fully in effect.

Maybe some random mulm came up with the gravel transfer and just took a few weeks to fully break down to the observed nitrates.
 
endlercollector
  • Thread Starter
  • #6
That does seem like a quick jump. However as has been stated nothing but h2o evaporates out of your tank so things like nitrates, salts, fertilizers, and other impurities will stay behind and become more concentrated over time unless you are topping off with with distilled water. A TDS meter is probably the easiest way to keep an eye on this (and at $10 it isn't much more expensive than the other random tests we have).

On the plus side the nitrate production shows that the cycle is fully in effect.

Maybe some random mulm came up with the gravel transfer and just took a few weeks to fully break down to the observed nitrates.

I'm going to have her test the nitrates daily this week and also keep topping off the water daily to see what happens.

I agree with Lynda.

The water evaporates, but the stuff in it does not. The more water you lose due to evaporation, the more concentrated those things become until eventually the water is too toxic for the fish. Top offs are extremely important to prevent high concentrations of toxic things in the water column.

I didn't learn about this until a few months ago as it was addressed in a Q&A in one of the Tropical Fish magazine issues.

I've been vague about topping off--letting things go down about 5-10%--not doing that again!

The only thing that evaporates is H20. That's why it's a good idea to use distilled water for refills. If you keep adding tap water with refills, whatever minerals it might contain will end up accumulating in the long run. In my first days as fish keeper I did just that, very few wc because all parameters were perfect, just topping off with tap water. And then my fish started dying. Took me a while to figure out why. This was before the days of the internet with all its readily available wisdom.

Otherwise, I had a very lousy chemistry teacher in high school, so I guess the nitrates would concentrate more in less water. 160 ppm seems a bit big jump from 20 the week before, though.

Do you have any decaying plant matter in the tank?




Good thinking, but wouldn't that in particular affect the ammonia and nitrite readings? That there's only nitrate should indicate that there are enough beneficial bacteria. There just seem to be too much waste products in the cycle.

Distilled water? I'd wondered about that and asked a while back in a thread about the Walstad method but was told to always top off with dechlorinated tap. It is a lot easier for me to do dechlorinated tap water--I really can't get enough distilled water for all my tanks

There was 1 anubias petite nana in there that had 1 leaf die during this process. I've since put it in the tank for phase 3. I just don't think there's anything else besides the Betta's waste contributing to the nitrate.

I'm no rocket scientist but I have to think the evaporation had something to do with it.

I'm confused as to whether you just tossed that sack into the tank or if there's a filter involved?

Maybe the sack is not allowing the water to flow through and so the beneficial bacteria is not populating there as it should be. Or, maybe you didn't get enough fabric.

It's a very tiny sack with a tiny bit of filter fabric shreds. The filter is an Whisper in-tank filter for up to 3 gallons. The pump has been pushing the water through without any trouble, BUT I did notice that the flow picked up noticeably when I topped off the tank for her. So I do think now that we have the following equation:

tank water - evaporation - filter flow = high nitrate
 
EricV
  • #7
I wouldn't expect the filter flow to have much bearing on nitrate levels. With the setup you've described there wouldn't be any denitrifying bacteria present. If anything the higher flow rate would deliver more waste to the BB allowing them to produce nitrate quicker.

That being said nitrate levels are dependent on waste levels more than anything. An equal amount of waste will produce an equal amount of nitrates regardless of the flow rate of a filter, the time frame may just be slightly different.
 
endlercollector
  • Thread Starter
  • #8
I wouldn't expect the filter flow to have much bearing on nitrate levels. With the setup you've described there wouldn't be any denitrifying bacteria present. If anything the higher flow rate would deliver more waste to the BB allowing them to produce nitrate quicker.

That being said nitrate levels are dependent on waste levels more than anything. An equal amount of waste will produce an equal amount of nitrates regardless of the flow rate of a filter, the time frame may just be slightly different.

I originally thought it would just be a question of the Betta's food intake and waste output, but going from 40 ppm to 20 ppm and then 160 ppm is just so off the wall. At any rate, I figured her counts would get stuck at nitrate, because there are no plants or soil, but I didn't think she'd get such irregular readings.

On the other hand, what can I say? My friend and I were the absolute worst team in our chem class. Our numbers were always completely out of synch with everyone else's. The teacher would make a nice chart showing a nice cluster of results, and then ours would be way off one the other side of the sheet of paper. Oh, yeah, and so here I am, helping our daughter with her science project because hubby the experimental physicist is too busy taking apart gold molecules
 

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