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Stocking Question for a 20 Gallon Tall


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Hi Everyone,

I have a well planted 20 gallon tall tank and was wondering how many more fish I could add without throwing off my water parameters. I currently do a 25% weekly water change and ideally wouldn't deviate from this with the new fish.

Here's my current fish/invertebrate list:

- 1 very chill male betta

- 6 harlequin rasboras

- 6 red cherry shrimp

- 4 amano shrimp

- 1 gold inca snail

- 4 nerite snails

- a few bladder snails that hitched a ride that I keep in check

I was thinking of adding 3 or 4 more harlequin rasboras or doing a small school (6ish) of another species (Neon tetras, chili rasboras, etc.). Do you all think that would increase the bioload too much? I know the rough 1 inch/gallon rule, but I figured that the invertebrates aren't impacting the bioload the same as fish do.  I attached a picture of the current setup.




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I think you definitely have room for more fish, but have you considered a small school of one of the smaller Corydoras species instead of another mid-water schooler?  That way you'd have a little more going on near the bottom of the tank.  If you went with Corydoras pygmaeus, while they also spend a lot of time on the bottom, they rummage around higher in the water column than other cory species.

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Well to partially answer your question my 20 gallon has 10 Harlequins and about 14 or so Otocinclus, 3 Mystery snails (larger bio load), 2 Nerites. My water tests 0 on the bad stuff (regularly 40 Nitrate, no idea why, fish don't seem to mind) pH hovers well at 7.6. I run 2 air driven filters. My tank has been running for over a year, I could potentially add a small set of schoolers if I got really ambitious and they'd likely do fine. (no plans to do that though). 

Your plants look fairly immature. How old is the tank? When was the last time you added fish or other occupants? 


Edited by xXInkedPhoenixX
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Thanks everyone for the advice and species suggestions.

Yes, this is a new tank only about 3 months old, so anything I do is going to be a slow process. That said, since it started cycling the parameters have been very stable.



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