Cycling A New Planted Tank - How Long Before I Can Add Fish?

tmjr

Lifetime Member
Lifetime Member
Nov 30, 2018
2
0
1
Calgary, AB
Hello all!

TL;DR: how long do I need to wait before adding fish to a newly setup 23G lowish-light tank planted with crypts/anubias/java ferns?

The full version:
I've just set up a 23G tank (a Fluval Vista 23) and have added (I think) lots of crypts, anubias, and java ferns. The lighting level is lowish (I assume) - a single strip of LEDs in the hood, that elsewhere indicates the PAR level is about 30. The substrate is Flourite Black Sand. I added peat moss to the floor of the tank before covering it with the Flourite.

I've started fertilizing as per EI guidelines, and have added Flourish tabs into the substrate. However, I'm just in the process of getting CO2 up and running due to some logistical issues; that should be up within a day or so. I 'seeded' the tank by putting gravel from a tank in the LFS and another planted tank enthusiast in my filter; no mulm though.

As I have little kids who don't care that much about the plants, how soon can I begin to add fish to this setup?

I've read elsewhere that a planted tank doesn't rely on a large bacteria colony to deal with ammonia and nitrites, as the plants absorb those things faster. As compelling as the argument I read is, I'm not knowledgeable enough to evaluate how correct the argument is. Those posts on another site stated you could add fish right from the get go, assuming heavy planting, and that the plants were actively growing. I think another assumption was that there were fast growing stem plants but that wasn't specifically stated.

So, I'm curious to know what the advice here would be: does a planted tank really need to wait for a complete 'cycle' before adding fish? More specifically, in my set up with low(ish) light and slow growing plants, how soon would do I need to wait/ what milestone would I need to reach before I could add some fish? If I didn't have my eager kids in the mix, I think I would crank up the CO2 and let the plants grow for quite awhile before adding any fish. But I've set up this tank partly so that my kids would get interested in the hobby, and for them its rather boring at the moment ( not for me though)! Consequently, I'd like to add a few fish (say 4 each of SAEs and otos to start) as soon as possible. I am also genuinely curious about the underlying science as well.

Thanks for your advice!
 
Last edited:

Lawless1

New Member
Jul 24, 2019
2
0
1
50
South Africa
If you use Seachem's Stability you can add fish immediately, i would use it anyway according to dosage instructions and maybe wait 2 weeks.
 

CarissaT

New Member
Jul 2, 2019
12
3
3
Canada
The concern of course is that ammonia levels stay at or near 0 for your fish and that your co2 doesn’t go too high for them. The plants themselves are going to have some beneficial bacteria on them already, and of course they also take up ammonia if growing and healthy. So I would say that once your co2 is stable and you see plants growing well, go ahead and add a small number of fish, test ammonia and see how it goes. If it were me to be on the safe side I think I would go with half of what you mentioned to start off (and no feeding). If ammonia stays at 0 for a few days then add another few, etc. Unless your substrate is producing ammonia, I don’t see the benefit in leaving the tank fishless for a length of time. You need something producing ammonia in order to keep the cycle going.


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