WolfPack21

Hello Everyone, my girlfreinds tank has just completed a fishless cycle (took about 3 weeks). Anyway, I was wondering if before we add fish should we do a water change? If so, how much? And also when should she replace her filter (out of her topfin 10 filter)? I don't like the idea of taking out the whole filter and replacing it with a new one because of all of the bacteria in that filter so what you do you recommend? Thanks!

omnitheforsaken

If you're going to replace the filter (I recommend an AquaClear), I would run the two filters simultaneously for a week or so before I decom the old one. Also, I don't see a need to change the water before adding fish unless there's something in particular that concerns you about the water.

Lucy

It would be a good idea to do a water change. I'm not sure about the amount, a guess would be 30-50% depending on the nitrates.
Does the filter media have carbon? If it doesn't, only replace it when it's falling part. You can just rinse it in tank water.
There's still bacteria on the decorations, substrate, sponge or bio-wheel. When you replace the media, it shouldn't have too much of an effect.
You can always keep extra sponges in your established tanks (for at least 2 weeks) and replace the old media with the seeded material.

Shawnie

congrats on the cycle!!!!
do you know your exact readings for nitrates? if they are under 20, and you dont have any waste on the bottom, you are good to go without a change...I wouldnt mess with that filter for a good 3 months and then I would only rinse it once a month after that in removed tank water....what are you stocking it with ?
lucy LOL

WolfPack21

Well the nitrite JUST dropped for her tank, so there is 0 nitrates right now. She plans on getting a dwarf gouarmi, cory cat, guppies, something along those lines. Thanks for the help! Also the filter from a TopFin power filter and I believe they have carbon in them?

Shawnie

do you have live plants? if not, the tank isnt cycled and the nitrite drop should have left you a nitrate reading without live plants....

top fins do have carbon ...you can just cut a slit in the cartridge and dump the carbon out after a few weeks of using it.....add some extra filter floss in with the cartridge that would have the filter media left on it

joy1125

don't add any fish yet, the tank isn't finished cycling ! It's considered cycled when you have 3 consecutive days of 0 ammonia, 0 nitrIte, and a nitrAte reading.

Good luck, be patient, it's almost there ! Also, when she does add fish, stock
s l o w l y. In a newly cycled tank, you don't want to exceed the fragile bioload.

WolfPack21

Oh good point! Yes, no plants and I'll wait a few more days untill I get a nitrate reading. Thanks for the heads up!

Shawnie

keep feeding the tank or it will die off and you will have to start over!

jprime84

I dunno, seems strange. I got my first nitrate readings while I still had a noticeable nitrite reading. The nitrite is oxidized into nitrate.

Imagine two cups, one labled nitrite and one labled nitrate. If you fill up the nitrite cup, and then pour that into the nitrate cup (to illustrate the conversion) at no point are both cups empty.

Shawnie

in a tank that is cycling, you SHOULD have nitrites and nitrates at the same time..(some have even missed the nitrites during this process)....once you no longer have the combo and just have the nitrates, you will be fully cycled...otherwise, you need to give it more time for the bacteria to process the nitrites...sometimes in planted tanks, you will NOT see nitrates as the plants eat them..but you should NEVER see nitrites in a properly cycled tank...

thorpbrian

If the cycle is proceeding correctly you should get your first nitrate reading as your nitrite readings begin to go down. Theoretically, once your ammonia readings have worked their way to zero your nitrite readings should have reached their peak and begin to fall, thus giving you nitrate readings.

jdhef

You get nitrite and nitrate readings when there is enough bacteria to convert some of the nitrite into nitrate, but not enough to convert all of it.

So basically you haven't grown as much nitrite converting bacteria, as you have ammonia converting bacteria. Once enough nitrite converting bacteria developes, it will be able to process all of the nitrite and your nitrite reading will drop to zero.

jprime84

I guess I wasnt clear. I am aware that there should be nitrite and nitrate values together at the same time at one point. That was what I was saying, in fact. If the OP has 0 nitrite and 0 nitrate readings, I think he will have to start over, as you should only have both at zero in a brand new tank.