Fishless Cycling - Help with readings

[TygGer]

I started to do a fishless cycle on my 46g tank with a raw shrimp on February 25th.

A couple weeks ago, my ammonia dropped to 0, nitrites about 5ppm and nitrates about 15ppm.

As the shrimp rotted away, my ammonia stayed at 0 and nitrites stayed constant at 5ppm. Nitrites would not decrease and my nitrates would not increase. I left everything alone for a couple weeks.

Last weekend I decided to put in another shrimp to help feed the bacteria. I tested for ammonia the next day and it increased one increment on the aquarium pharm. chart.

Today, I re-tested and ammonia is 0, nitrites is 0 and nitrates is about 5ppm.

How can nitrates decrease? I haven't done a water change.

 

[fambrough]

I can not tell you why the low nitrate reading. However, test kits convert nitrites into nitrates when testing for nitrates only. Therefore, your readings of nitrates during the cycle (presence of nitrites) will not be accurate. Check again just to be sure of your reading. It does sound the tank is completely cycled. I just went through this process, but am no expert. I hope someone with more experience will chime in for you.

Best of luck,
Ben

 

[TomK2]

yes! a test kit measures the amount of nitrate by how much nitrite it can be converted into. So, when you have large amounts of nitrite, and you run a nitrate test, some of the nitrate you thought you had was really the nitrite that was there.

Here's a link for some info:
http://home.comcast.net/~tomstank/tomstank_files/page0018.htm

 

[TygGer]

I see... that makes sense then because I saw nitrates almost immediately when I detected nitrites.

The first shrimp has completely vanished. The second shrimp that I put in a few weeks later is now a big fuzz. A couple days after putting it into the water, my nitrites went to 0. That's strange how it dropped so fast all of a sudden.

I still can't understand why I test 0 for nitrates. I'll test again later this evening.

I hope Im completely cycled. It's been about a month now and I cant wait to add fish. I just dont to kill the fish by adding them too early. That would mean that this whole time cycling fishless was a waste.

 

[TomK2]

Sorry I didn't read your original post carefully enough, and didn't catch the dilemma of the nitrate values decreasing.

The test kit chemistry can explain why you might think you have nitrate, when in fact you really have nitrite. However, the nitrate test can be thought of as the sum of nitrite and nitrate, and should be the same over a short period, after all, any nitrite that disappears because of bacteria should bee seen as the nitrate it was converted into, barring any absorption or use by other living things (plants?). so if your nitrIte is 5 ppm or higher off the scale, when it disappears you should have nitrate 5ppm or greater on the nitrate test. I am not aware of anything other than plants and algae using up the nitrogen to any apreciable amount. I don't think the nitrifying bacteria absorb the nitrogen to any apreciable extent. So yes, you do have a mystery in the disappearing nitrate.

Unless you have plants soaking it up, the only explanation is test kit error. The AP nitrate kit is tricky, and the bottle and test tube agitation steps are explicitely described as "critical" in the instructions. User error is always possible (I know I have messed up a number of times). But if you have no ammonia, no nitrite, and nitrates have increased over your tap water values, you should be done. Any doubts, have the test confirmed at a LFS or a friends kit. Enjoy your new fish!

 

[TygGer]

I just re-tested and here are my results:

ammonia = 0
nitrite = 0
nitrate = 20ppm

I guess I must've messed up the nitrate test last time. The water looks a little cloudy. Does that mean anything?

Tommorrow I'll remove the fuzzy shrimp and do a 50% w/c before buying fish. Should I gravel vac?

It's been many, many years since I've done a cycle and this is my first fishless cycle.

Thanks!

 

[Jchillin]

The cloudiness is most likely a bacterial bloom, which is common in a newly cycled tank. It will clear up after a few days. Not to worry. You don't need to vac the gravel as yet (not a whole lot of detrius in there).

Go get the fish...hurry...LOL

 

[TygGer]

The bacteria bloom won't hurt the fish?

 

[TomK2]

nope. the water will settle down in a few days. Enjoy your new tank!

 

[TygGer]

Great! I'm going to do a 50% w/c without vacuuming the gravel when I get home today. If I don't have fish by today, then definitely tomorrow!

 

[carpediem]

Congratulations, TygGer. You did it. That tank has been testing your patience. Good for you for sticking it through.

Have fun with your tank. Have you decided on fish yet?