29 Gallon Tank Aquarium cycling, nitrites, and soft water


Hey all, bit of a noob here. Here's the full back story so I can cover as many of the details as possible.

Bought a 10 gallon tank (standard crappy TopFin starter kit from PetSmart). Did some research on cycling before getting fish, and landed on getting six Zebra Danios. No live plants, but plenty of half height fake plants and decorations (treasure chests, etc) for them to hide in and around.

Before getting the fish, I went through the cycling process (as far as I could tell) for roughly a week and a half. I used Top Fin water conditioner every time I added/changed water, and Tetra SafeStart plus (full 8 oz bottle first time I filled the tank.) I used the API Freshwater master test kit to check levels at least once a day. (For GH and KH I used the API test strips.) Every bit of water that comes into my house (including outside faucets, according to my measurements) is softened with a RainSoft EC5 water softening system. I live in Cincinnati, OH in the US.

On day 1, these were the numbers from the conditioned tap water:

pH: 8.0
GH: ~30
KH: ~60
Ammonia: 0
Nitrite: 0
Nitrate: ~5

I know these numbers can fluctuate, so I've been testing my tap water at least every 3 days or so alongside my normal tank water testing to see how consistent they are. The numbers from both inside and outside water faucets remained extremely close to these numbers at every testing. The only deviation I ever saw was the pH ranged between 7.5 and 8.8 or so. The temperature inside the tank itself was kept at 72F.

While cycling the 10 gallon, I used several drops of an ammonia hydroxide solution (4%) I got off of Amazon (this stuff isn't easy to find haha). Within a few hours, this brought the ammonia in the tank up to around 0.5ppm, and everything else stayed the same. Same numbers the next day, 0.5ppm ammonia, 0 nitrites, same nitrates as the tap. The next day, however, ammonia was down to around 0.25ppm, nitrites still at 0. Nitrates were up over 10ppm (tap was still at 5ppm). On day 4, I added a few more drops of the ammonia solution, getting the concentration in the tank up to about 0.5ppm again. Next day, ammonia was down to 0 as far as I could tell. Nitrites still 0. Nitrates, however were definitely between 10 and 20ppm. I added a few more drops of ammonia on day 6, and by the next day, they were back down to 0. Nitrites continued to remain at 0. Nitrates were definitely at 20 - 40ppm at this point. I did about a 50% water change and added a few more drops of ammonia. It went back up to 0.5ppm, and less than 24 hours later it was at 0. Nitrites remained at 0, as they had the entire time thus far. Nitrates were back up around 10 even after the 50% water change.

At this point, I bought some fish. I took my daughter to Petsmart with me, and we asked for six zebra danios (some glowing, some not). The guy ended up giving us seven, because he didn't want to try to catch just one to put it back. We got them home and did the float-the-bag-for-a-while thing to get them acclimated. After about an hour I opened the bag up and gently netted them out one at a time to move them into their new home. Waited about an hour, then took some water readings. Same numbers as the day 1 readings I posted above.

I didn't feed them until they'd been in the tank for 24 hours, and I gave them some flaked food that I crushed between my fingers. Seemed like barely any food, but I didn't want to risk overfeeding. In retrospect, I got a bit lucky, as the amount I gave them was roughly one danio-eyeball-sized flake per fish. I kept taking water readings, and didn't feed them more than once every 24 hours. Water readings stayed the same throughout the first couple days. On day 3, I noticed that ALL of them had noticeably red gills. That may have been happening sooner, but it wasn't something I was aware of to look for. Being a noob, I panicked, and went out and bought ALL the things. Melafix, Stresszyme, Pimafix, General Cure, you name it. I wish I remembered how much of each I administered, but it was a rough few days. (For the record, this was over a month ago, and all the danios are still alive.)

My worst mistake came a few days later. I took the replaceable filter cartridge out of the filter and threw it away. (Yep, I know. I wish I would've known then.) I added a new cartridge, and much to my dismay, the next day their ammonia was up over 1ppm. Nitrites still at 0, and nitrates remained the same as the tap (5ppm). I added another full bottle of Tetra SafeStart plus, and I've been doing 30% water changes every day, while only feeding once per day. Pretty sure my cycle completely reset and now I'm playing the waiting game. I've never let their ammonia get over 0.5ppm, and I condition the water with Seachem Prime now, instead of the TopFin conditioner.

Now I want to jump back in time to about three weeks ago, when I came to the realization that 10 gallons wasn't really enough for seven of these zippy little guys. I decided that a 29 gallon was the most reasonable size for the room the aquarium was going to live in, and picked up the same TopFin starter kit, but the 29 gallon size. I know it's not the best in the world, but with some modifications, it's not terrible. Same general setup, fake plants, few bags of gravel to cover the bottom, various decorations (no driftwood or anything like that), 12 inch air stone turned almost all the way up via the pump. The main change I made was to completely remove the carbon filter cartridge and just pour as many fluval bio rings into the filter that would fit.

I went back to using the chlorine/chloramine only water conditioner (instead of the ammonia neutralizing Prime), and added 16 oz of Tetra SafeStart plus. Testing the conditioned water on day one yielded the same numbers as my original day one numbers way up above there. I added several drops of the ammonia solution to bring it up to ~1ppm within a few hours, and I was elated to see that the ammonia was nearly 0 the next day. And there were nitrites! Way over the 5ppm that's readable on the API test, but still, nitrites! I did the same the next day, and the ammonia all but vanished in a day. Nitrites were still high, but now my nitrates were around 20ppm.

Fast forward to the present day, and I can still add ammonia up to 1ppm, and watch it disappear within 24 hours. My nitrates are currently at 80ppm, and my nitrites are off the chart (well, bright purple on API master test kit, which doesn't match up at all with any of the colours.)

I want to get these little guys moved over to the bigger tank as soon as possible, but the nitrites are a bit befuddling. Do I just need to wait? Should I do water changes to bring nitrites down? Does water softening play into this at all? (I did add a 1/4 tsp of baking soda to help with the softened water last week.)

I've seen a lot of reports about not letting your nitrites get too high, but others say it's fine you just have to wait.

Wow, I apologize for the wall of text, and I appreciate anybody that read through all of this. Just trying to leave nothing to interpretation (to the best of my recollection, of course.)


Hi there,
First off Congrats on your new fish. Don't stress about the Zebra Danios. A ten gallon is fine for them. So for me while doing a Fishfull cycle my Ammonia was at 0 PPM and my Nitrites were at like 3-4 PPM. (nitrates at 15 PPM). I did one water change (50%) then added Aqueon Pure Beneficial Bacteria, API Quick Start, and SeaChem Stability. Within a day or two my nitrites fell to 0 PPM and my tank was fully cycled. So yes, id recommend a 50% water change and bacterial supplements. Although remember I had a Fishfull cycle and you did a fishless cycle, so you may have to play around with the ammonia if things aren't going to 0 PPM.
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Just keep tans on the parameters. Test daily even multiple times a day. after a week or two you should know that your tank is okay.
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