Questions regarding bioload

[chooz]

Hi All,

I have a small tank, 35cm x 22cm x 30cm (length x width x height). I am using "waterfall" type external filter, no extra lighting (aka I am using ambient room light only, near to window), and 1-5 mm size gravel. I don't intend it to be a planted tank, so I am using artificial plant only. Currently I have 4 tetras in there for more than 1 month now, so the nitrogen cycle should have been established.

Here are my questions:

1. With such a small tank, what else can I add in (given the conditions above)? Or what is the maximum number of small fish (<5cm) before it is overloaded?

2. Fish like tetra, guppy, barb, etc need to be in a shoal, right? That means I can only have one single species of fish in the tank at one time, right? Is there a minimum number in a shoal?

3. Can I add in just two small albino corydoras? Are they solitary or shoal fish?

4. What solitary fish can be added? Gouramies? angelfish?

Thanks. Hope I learn from you guys and make this a meaningful hobby.

[Quixotic]

What are the tetras you currently have?

1. Depends on the potential size of the fish you intend to add. Since it is not a planted tank, I would suggest less fish, and go with no more than 10 fishes (< 5cm in size) including the fishes you currently have. If you want to stock more, you may need to have better filtration or perform water changes more frequently (more than once per week).

2. Generally, yes, the larger the number the better they school. Considering your setup, perhaps you can go for another species of tetra, but select one that is of similar size to the ones you currently have.

3. Corydoras do better in groups, six is the ideal number. However, you can still keep them in lesser numbers. Another point to note is that the "small" albino Corydoras are probably juveniles, they do grow big and depending on species, may not be suitable for a small tank like yours.

4. Angelfish will outgrow your tank easily, so that will be out of the question. Smaller gouramies may work though, but again, you need to watch the bioload.

Just some ideas on the stocking, excluding your current tetras:
a. 6 x same/other tetras of similar size, or
b. 4 x same/other tetras of similar size, 2 x dwarf gouramies, or
c. 4 x same/other tetras of similar size, 4 x dwarf corydoras (Corydoras habrosus/pymaeus/hastatus)

[chooz]

Thanks for the informative reply.

The 4 tetra that I am having now are 2 black tetra and 2 jewel tetra.

Another question: would a betta be safe from fin nipping if there are tetras around. One of my black tetra seems to be chasing everyone else around.

[Quixotic]

Oh, the 4 tetras are different? Not really sure what the tetras are, going by these fancy names, but I would suggest to get more of these 2 species then, increase their numbers up to at least 4 or 5 each.

I do not suggest adding a Betta. The number of tetras in there are too few. So when they nip each other to establish pecking orders, they may get your Betta involved, which is why you need a larger school of them to diffuse the aggression and keep each other busy. Even then, there are no guarantees they will not take a liking to the Betta's nice fins.

Actually, tetras generally prefer some amount of current in your tank, while Betta prefers water with not much flow. So if you want to keep them, just be mindful and not introduce too much strong currents in your tank.

[chooz]

The black tetra is Gymnocorymbus ternetzi

The jewel tetra is Hyphessobrycon eques

I got the scientific names from FishBase, not sure if they are correct but at least the fish in the pictures look like the ones that I have. I am not seriously thinking of putting a Betta in; I am just exploring the possibilities for a small tank. I guess I will just stick to your suggestions above for the time being until I can afford a larger tank and setup.