Adding fish into tank that had fish that moved out?

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I've moved the fish that were in a 20 [acronym:d4c776b42f="Gallon"]gal[/acronym:d4c776b42f] to a friends tank that had the extra room for them and I new they were going to have to moved into a bigger tank in the near future. Having changed my mind on more tanks I thought they would be much happier with more swimming room. I've also decided on the fish I want to keep in this tank as it looks like it'll be my only one. The fish that moved out were some tiger barbs and serpae tetras for now. There is still a red-tailed shark in the 20 [acronym:d4c776b42f="Gallon"]gal[/acronym:d4c776b42f] but part of my question is will he be ok with the fish I want to add. I want to add some guppies and dwarf gouramis and my first question is would they be ok with the shark? The next question is that since the tank has been up and running with all the fish for roughly one month now, do I still need to intro small numbers of fish at once or could add all the guppies and then later the gouramis or even all at once. The tank has had a 20% water change since the fish were removed but the filter has lots of bacteria built up and the water is testin good. Any thoughts on the combo and intro would be great!! I should also note that the shark could move top the other tank aswell since he will get to a fair size but if he works that'd be great too.

[TankGirl]

I do not have experience with the red tail shark, but from what I understand they are relatively aggressive, but mainly with their own kind. Guppies might be pushing it. Dwarf gouramis can probably handle themselves.

Your good bacteria are present in numbers based on the amount of ammonia (food for them) that is present. When you removed the fish, the bacterial colonies decreased due to the reduced ammonia in the tank. I think this die-off takes a couple of days, but I am sure you are "cycled" for the red tail only by now, and you will need to add more fish gradually, or get Bio-Spira and add them all at once. It is good that you thought of this, because I don't think a lot of people would have thought about it at all.

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Like I said I might very well move the red-tailed out if there is any chance he would go after the guppies. It's only been about 6 hours since the fish left and was hoping to add some fish tonight. Does the "bio-spira" really help either way and also how big do most guppies really get? I've read anywher from 1" to 3". I've never seen them at three inches so just curious. Also same question on the dwarf gouramis, is 2"-2-1/2" a fair number for them. Thanks for the responce tankgirl.

It's only been about 6 hours since the fish left and was hoping to add some fish tonight.

You have a few days before the bacteria numbers will drop significantly. you can buy the fish you want this weekend, no problem.

also how big do most guppies really get? I've read anywher from 1" to 3".

I've never seen a 3" guppy either, maybe a little over 2". Not certain on the dwarf gouramis, never kept them.

When the redtail gets bigger, he might eat full size guppies, but that would take a while. Guppy fry, most fish will eat guppy fry.

[Christmasfish]

Your gourami are not going to like your shark if one of the males sets up housekeeping. The females can be real stinkers when in a pack (not shoal, not school...PACK). Your redtail has the advantage of having his digs staked out. Dwarf gourami are not as peaceful as blues or pearls. They can be pretty rough on each other. I have dwarf gourami and assumed they were like the gourami my grandad kept. Nope. They are stinkers. My female had no dorsal rays by the time her tank mates and later the male here were through. The male shaved her scales like a grater.And nearly took an eye.
The guppy dither fish may be great for them. Larger daring tetras may be better? Tetras like the same soft acidic warm water at least.
There are small interesting gourami like croaking gourami that are much more passive and community friendly. Some odd large community bettas too. Most are not always colorful when captive, tho.

[TankGirl]

It's only been about 6 hours since the fish left and was hoping to add some fish tonight.

Sorry, I though it had been a couple of days.

The dwarf gouramis get to be about 2.5 inches, and they are not peaceful, but given enough room they do okay. I think Allivymar kept 3 in a 10gal but when I have kept one in a 10 they generally have killed their tankmates, or seriously harrassed them (I had 2 separate tanks that this happened in).

Good advice from [acronym:aa7ef0ccf5="Crushed Coral (if substrate) or Counter Current (if referring to a Protien skimmer) or cubic centimeter (if referring to a measure of volume)."]CC[/acronym:aa7ef0ccf5] and Christmas fish, to which I can add nothing!