How Do I Select New Fish

[soritan]

So, I have an existing tank, with existing stock. How do I research my tankmate options for this tank? What are the basic steps?

I prefer you answer this tank question (where did that typo come from? Freud? Where are you?) generally, so that I can learn how to research on my own (and others can learn how to do so, as well). But if you want you can address it to my specific circumstance, and that'd be appreciated, too:

Tank size: 20 US gallons, tall (24.25" x 12.5" x 16.75")
Filtration: 1 Aquaclear 20 (100gph), 1 Biowheel 125 (125gph), 1 Hydro sponge filter.
Cycled?: Yes
Tank maturity: 5 months
Current stock: 19.49" of fish -- 6 Harlequin rasboras, 3 White cloud mountain minnows, 1 female betta (aggressive to pale colored fish), 3 Schwartzi cories
Heavily planted?: Yes, very much so. Crypts, anubiases, water sprite, and anacharis.

I feel I could comfortably handle another 5" of fish, in layman's terms. Mostly I've been looking into simply buying a few more Schwartzi cories and a single Apple Snail, but as I have plenty of time before that actually happens, I'm reading up.

 

[dwarfgourami]

Well, first I'd be looking at upping the number of any schooling fish if needed.

Then, if that left space over or was not needed, I would make a list of narrowing down factors:

I would be thinking about size. In a 20 gallon tank, with limited room, you are not going to be able to introduce anything much over 3 inches, nor a new schooling fish unless it's really tiny. So that narrows it down.

I would think about how much filter space I might have left- i.e. if I already have one messy pooper in a smallish tank, I might exclude adding another.

I would think about temperatures. In your case, you've got WCMs, which need cooler temperatures, so I would exclude any warmth loving fish. (how do your Scwartzis get on?)

I would also think about the general atmoshere of the tank: are the fish already in timid and slow-moving or active and zippy? I would make a mental note to try to preserve that.

I would also think about where in the tank I have space leftover- are my current fish mainly surface or bottom dwellers? I would be particularly careful if I had fish that were likely to be territorial about one particular area of the tank.

I would think about whether current fish are either potential fin-nippers or potential victims of fin-nippers.

And anything else, like you say your female betta can't cope with pale colours.

With this list, I would go to the lfs with a notebook (but no money!) and/or sit down with the biggest aquarium book I could find. Every time I saw a fish I liked I would run it against my checklist.

So in my case, for my next tank I've ended up with a list that looks like this (the "given fish" are a trio of pearl gouramis and a pair of bristlenoses+ a school of tetras):

no zippy fish- the giant danios had to give

not too much competition on the surface- again the danios are out

quite warm water- a number of attractive goodeids drop off here (sob)

no fin-nippers- again, excludes a lot of goodeids and the gambusia holbrooki

nothing big enough to eat the tetras

So with that in mind I can go out looking.

 

[soritan]

Well, to answer your question (and skip the other Extremely relevent points), my Schwartzis are cool, and my WCMM are brand spankin' new. Before I bought them, I had read so many articles with so many wild opinions on their care, that I decided to give them a go, even though my tank tended to be on the warm side. I have a heater in there, but it never turns on. Why? Because it's a planted tank, and with the lights on 14 hours a day, the tank is never cold.

I highly suspect that my previous plan (adding 2 more cories and 1 apple snail) is the perfect plan for me, but I wanted to know how to research for future plans.


For my specific circumstance: I know for a fact my female betta kills inverts (African Dwarf Frogs, Shrimps, the like), and I know she harrasses many fish, with specific interest in fish colored simmilar to her own coloring (pale). I still yearn for one or two other fish for variation. I'm thinking for my circumstance, that maybe I'm right at my limits as far as fish species go, but not at my limit as far as "inches" go (with the 3 filters and heavy planting).

I just wanted to start a topic that I know I, myself, would have found useful at the very beginning, when I knew that I wanted a specific type of fish (in my case, Betta splendens), but didn't know about other tankmates.

 

[dwarfgourami]

I didn't really mean to quiz you about your tank, but more think about as many relevant points as I could for the potential newbie you had in mind. I'm sure there are loads I have missed. But that is what I would do- and am still doing: settling on one or two must-have species and then listing all the exlusion factors they bring with them.

 

[soritan]

Yup, trying to make it so that a n00b can read it and figure out on their own is my ideal.


My tank?
I find myself looking at what I have, looking at the most aggressive fish -- in my case, a Betta splendens (female) -- and attempting to locate what won't piss her off. I halfway suspect that she's NOT aggressive to pale colored fish (due to a disease that is obvious in tankmates to fish I had assumed she'd killed), which is what's driving me to research other fish.

I guess a useful thing to know, would be the different familes of fish available, or maybe a link to definitions of species/climes availble.

Another basic thing to know (which I see often mucked up), would be the cold water/ tropical thing.

Goldfish are not tankmates to 89.999% of what's available on the market, etc.