is my tank ready for fish??


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Jun 14, 2024
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Mountain View California
Hi! I am new and excited to have found this place!

So I recently set up a 20 gal long tank that has been cycling for almost 6 weeks... I have been testing the water daily and it looks like things are reaching an acceptable level now. Maybe even enough to be done? I am hoping to add fish by today or at least by the end of this week. My concern is that the nitrate seems a little abnormally high... or is it? Would love the opinion of a more experienced fish keeper. And just for some background, I am planning on doing a little community tank with a betta and 7 tetras! (Also any tips on this would be super helpful its my first tank) I have attached a photo below of today's test. I think ammonia and nitrite are fine. It's just that darn nitrate! Also I just did a water change yesterday! If it is too high what can I do to lower it at this point? Thanks so much.
Ammonia and and nitrites look OK. Nitrates look to be somewhere around 15PPM which is fine for most fish but not all.

Would need to know the PH level and GH and KH levels as to advising fish. Still I will advise in general as to having a beta in a community tank. It flat out normally does not work. Beta's are very territorial and will often attack other fish in a tank. I would think that having tetras with a beta could also be bad for the beta as many tetras are fin nippers. What species of tetra are you interested? I've never been much into tetras but neons, black/white skirts seem pretty OK for a community tank but just keep in mind that not all tetras are suitable for a community tank. As an extreme example a piranha is a tetra.

Regardless of all the above we wold still need more water conditions such as PH, KH and GH before beginning to give stocking advice. You can often get the GH and KH levels from your water supply website.
Thanks for this. I have heard a lot about community betta tanks but honestly it sounds risky... but is there a different kind of school fish that would be better than tetras? I just want to make use of the space. If not I guess my betta will get it all to himself! My PH is at about 6.4-6.6 which I think is a little low? I don't know how to get info on the KH and GH but given that it will likely be just the betta now (and maybe a snail) is everything ok?
A tank is cycled when it can clear a 3 ppm dose of ammonia to zero ammonia and zero nitrite in 24 hours.
Without knowing how much ammonia you've been adding to cycle the tank we cannot say if it is now cycled.

Nitrate builds up when doing a fishless cycle with ammonia as that's the end product of the nitrogen cycle. That's why the cycling method on here says to do a very large water change at the end of the cycle.
However, there can be nitrate in tap water so it's a good idea to test tap water for nitrate to see how much tank nitrate is being made in the tank and how much is coming from tap water.
Hello. You have a small tank, so the water chemistry can change quickly if you're not careful to remove and replace at least half the water a couple of times a week. Changes in water chemistry makes for unlivable conditions for your fish. You can increase your chances of success by keeping the size of the fish small and by not keeping too many.

What kind of filter are you using? I have been using chemical filtration to help reduce nitrates, and it has been working out. I put SeaChem Purigen and Fluval Clearmax media in my filter. I started using the chemical filtration media since large water changes weren't totally eliminating my nitrates.
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Hello again. You know you could have just the small Tetras. Bettas are on the aggressive side. You could acclimate the Tetras and simply change half the tank water a couple of times a week to keep the nitrogen out of the tank water. I would use a good water treatment and bacteria starter like the products from API. I've used them for some time when starting up a new tank.

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Thanks for all this it is super helpful. Through your advice I was able to lower the nitrates to 5ppm! NOW its the ammonia... it is sitting rigidly at .25ppm and I cannot for the life of me figure out what is wrong! I have not dosed in days and have been doing several water changes to lower the nitrates. I was thinking I went over bored and killed my BB through all the water changes? If anyone could provide insight on what to do in this situation it would be so helpful... I hope I haven't screwed up the cycle

As for the filter I have a sponge filter. It works great but does get very dirty.
Water changes don't kill the bacteria; they live in the biofilm which is tightly bound to surfaces. Maybe if you did not remove any chlorine or chloramine from the water using a water that would stop them growing, but that would only happen if you didn't use a water conditioner.

Can you tell us exactly what you have done to cycle the tank, please. This will allow us to see if you've missed something.
So I started out by using fishfood as my ammonia source but it wasn't really working. After about a week I got the Dr. Tims ammonia in a bottle. I dosed 80 drops to bring the ammonia to 2ppm. Once it started converting to nitrite I only dosed enough to bring it back up to 2ppm. Some days I didn't dose if the ammonia or nitrite was too high. Once I got a tace of nitrates I started dosing less. Eventually I got the ammonia/nitrite to a respectable level and then the nitrate spiked alot so that is when I started doing a lot of water changes and holded off on the dosing to get things under control. As I said previously my ammonia spiked. But after I tested today it looked as if it had converted to nitrites...

When I was doing my water changes I would add water directly from the tap and then add prime once the tank was full. I didn't think the chlorine could cause damage over a short period of time like that but I could be wrong.
Don't know how much difference it makes when doing a cycle but I always add the water conditioner before adding the water to the tank. Now, if fish are in the tank, I would not even consider adding unconditioned water.
When fishless cycling with ammonia (including Dr Tim's ammonium chloride) the only way to be 100% sure you've grown enough bacteria is to add a dose and test for ammonia and nitrite after 24 hours. If they are both zero it is cycled. If one or both are not zero, the tank is not cycled. The fact that your nitrate increased indicates that you have some bacteria, though it cannot say if there are enough of them yet.

The method on here recommends adding enough ammonia to get a reading of 3 ppm. Dr Tim's method says 2 ppm as he uses a different scale for measuring ammonia - like there are 2 scales for measuring tank length, cm and inches.
I don't know if you've found our method for fishless cycling so I'll give the link
I would like to know if there is anyone on earth that can see a difference in the colors of the API Nitrate 20ppm and 40ppm.
I've passed every color recognition chart they ever tested me with. I even took a pic and downloaded it to the computer and
changed the contrast and still can't tell.
Nitrate is the least accurate of our home testers. It is best use to measure a change rather than an absolute level - has nitrate gone up since I last tested? Is it the same or higher than my tap water level?
The important thing is that the level is below 20 ppm when there are fish in the tank as this is nowadays accepted as the highest safe level for fish.

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