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-   -   Max number of fish in a 20g tank? (http://www.tropicalfishkeeping.com/characins/max-number-fish-20g-tank-130364/)

suzib 03-01-2013 10:15 AM

Max number of fish in a 20g tank?
 
I set up a new tropical fish tank, just over 5 weeks ago and have slowly been adding the following fish:

5 x silvertip tetras
3 x rosy tetras
3 x lemon tetras

I want to add a few more rosy and lemon tetras, but would also like to add some different kind of fish. When I first bought my fish, I asked the guy in the shop for advice and he said to start off with a few tetra fish, because they like to be in groups. I thought he meant any kind of tetras, so bought 1 silvertip, 1 rosy and 1 lemon. They didn't look very happy together, to begin with! On further reading, I realised I should have bought 3 of the same kind, but the guy in the shop didn't suggest this to me at the time of buying the fish. I wish he had though, because I now feel I have to increase the numbers of each type of tetra, because they're clearly happier in a group, but I'm worried it might restrict the number of other type of fish I can buy?

Byron 03-01-2013 11:59 AM

First off, I would like to welcome you to Tropical Fish Keeping forum.:cheers:

Now to your 20g tank question; you do not have room for more species. I would however increase the Rosy Tetra and Lemon Tetra to 6 (Lemon) and 7 (Rosy). Keep an eye on the Silvertip Tetra in case they fin nip.

Tetra are shoaling fish, meaning they occur in very large groups. The must have a group for several reasons which can include security (less stress to the fish), social interaction, hierarchy, etc. Studies have shown that when shoaling fish are in groups less than 5 or 6, they often become more aggressive. This is due to stress, and it weakens the fish.

There is not a lot of space in a 20g, but you will be OK with these three species if you perform weekly partial water changes. Live plants help a lot, even if as simple as floating plants.

We have fish profiles, second heading from the left in the blue bar across the top, and if a name is used identical in a post as it appears in the profile it will shade, as those above did, and you can click that link to the profile.

Byron.

suzib 03-02-2013 06:47 AM

Hi Byron, thanks for your lovely welcome and reply!

I had a feeling I might not be able to add new species to the tank, but was kinda hoping it might be possible. Never mind. I will definitely add more Rosy's as the current ones are hiding a lot and not eating so well. I added 3 silvertips, 1 rosy and 1 lemon a few days ago and would like to know how soon I can add more? Also, how many can I add at a time. I've been adding 3-4 each week so far.

Thanks!

Byron 03-02-2013 05:00 PM

Quote:

Originally Posted by suzib (Post 1451191)
Hi Byron, thanks for your lovely welcome and reply!

I had a feeling I might not be able to add new species to the tank, but was kinda hoping it might be possible. Never mind. I will definitely add more Rosy's as the current ones are hiding a lot and not eating so well. I added 3 silvertips, 1 rosy and 1 lemon a few days ago and would like to know how soon I can add more? Also, how many can I add at a time. I've been adding 3-4 each week so far.

Thanks!

Do you have live plants? These serve two purposes: first, they break up the space and the fish will be more relaxed (esp the Rosy Tetra, more below), and second, they assimilate a lot of ammonia. This impacts the number of fish that can be introduced.

The Rosy Tetra are quiet fish that do not like bright light nor water currents, so they will always remain in the quietest and dimmest part of the tank. When you have lots of plants, they will be more relaxed, less stressed (= healthier) and show their brightest colouration.

Byron.

suzib 03-02-2013 05:12 PM

I have 4 live plants and 3 fake ones. I carry out a water change once a week and add Nutricycle each time. The water tests seem fine so far.

What kind of food is best for the Rosy's? I have been giving them flake food, but have noticed that the Rosy's aren't keen on swimming up to eat it - would switching the light off during food time help, if they don't like bright light? Not sure what to do about the filter current though!

Thanks!
Posted via Mobile Device

Byron 03-02-2013 05:24 PM

Quote:

Originally Posted by suzib (Post 1451809)
I have 4 live plants and 3 fake ones. I carry out a water change once a week and add Nutricycle each time. The water tests seem fine so far.

What kind of food is best for the Rosy's? I have been giving them flake food, but have noticed that the Rosy's aren't keen on swimming up to eat it - would switching the light off during food time help, if they don't like bright light? Not sure what to do about the filter current though!

Thanks!
Posted via Mobile Device

This is part of the "settling in" issue. I have a group of these fish and they are rather timid. If I sit still in front of the tank after feeding, I see them begin to venture out more and even surface, sometimes. I would not turn off the light, as you want the fish to settle and get used to things being "safe" for them.

I wouldn't keep adding the Cycle, it won't eactly do any harm, but it also isn't necessary, and the live plants will deal with the nitrification best. Don't know what plants you have, but some floating would nhelp both issues considerably. Water Sprite is ideal for this [click the shaded name, it is in our profiles with photos], and Brazilian Pennywort is a second choice.

How much current is there? The main things is that the fish must be able to get out of the direct current, otherwise they will be fighting it 24/7 and that really wears them out.

Byron.


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