[minorhero]

Hi all, new to planted aquariums and to this great site!
I started by buying a 37 gallon tank (22” deep, minus a few “ of substrate), putting down some carib eco complete substrate, and got planting. My goal has been to do what I guess would be considered a “silent cycle.” Basically I just planted several, fast growing plants, mostly stem plants, and provided them with root tabs and seachem flourish, as directed. I also added a somewhat decent LED light (keeping it lowtech, no CO2, plants only need low to moderate light). It’s been just one week now, and I detected maybe 0.25ppm ammonia, somewhere between 1-5ppm nitrite, and ~5ppm nitrates. I haven’t added any source of ammonia, so I’m thinking that the tank is sort of doing it’s thing with the plants alone? Im wondering if I should do a small water change soon if the nitrites don’t go down and if ammonia climbs? I did also add some API quickstart once I saw those levels, to see if that would do anything to help speed up this process. At this point, if plants continue to grow and if nitrites go down, would it be safe to add just a few fish at first, after a partial water change?
Thanks!

You should have a source of ammonia to get a good cycle. You don't want a situation where you have grown some nitrifying bacteria but not enough to handle the waste fish produce, then when the fish get added you get immediate ammonia spike and have to re-cycle your tank. Your ammonia could be as simple as some fish food you let rot or it could be a pure ammonia product.

Keep an eye on the stem plants, despite claims on the bag, eco-complete is actually inert. The only fertilizer it had was whatever was in the water in the bag and as you might imagine that goes away pretty quick. So if you plan to proceed with only root tabs be aware you should be replacing those on some kind of regular schedule. Personally I prefer liquid fertilizer all in one product like Nicolg ThriveC or Aquarium Co-op Easy Green. I actually have both in use on different tanks and they both do a fine job for me. As for water changes. You can do one whenever you feel you need it. The plants by themselves can handle reasonably high levels of ammonia, certainly 4ppm won't do them harm. Fish of course are a different story.

 

[minorhero]

Thanks for the reply! I’ll be sure to replenish the root tabs as they recommend as well. There’s actually a really interesting aquarium co-op video that mentions starting a new tank without ammonia and just using plants, since you’re essentially mimicking their natural habitat (but I do realize that this requires the tank to be fairly heavily planted). Im wondering if this will suffice because if the plants are eating everything up, then in theory I don’t care so much about the bacteria. And in theory they should and will still grow as well. I am curious to check my levels tonight after work to see if nitrites have to still spiked and if ammonia has gone up/down.

Plants as source of ammonia requires a lot of plants because in this situation, the decaying plant matter (dead leaves, stems that don't make it, roots that die off etc) are what is producing ammonia. In order for the plants to be the ones to eat any ammonia fish create essentially requires a LOT of plants and very few fish. It can definitely be done but its also not accurate to say this is the natural environment since in the natural environment, there is also loads of beneficial bacteria AND the water in streams and a rivers is being constantly 'changed' at rates that are really quite impossible in home aquariums. In function though if you were to say plant a tank and then add one or two fish you would actually just be doing a fish in cycle which is fine and all, but its not really the same as just letting the plants do the filtering.