What’s the rule for keeping which fish with which fish?

[hihello405]

I already have a goldfish tank, and planning to get a tropical fish tank. Both of them are 10 gallons. I know goldfish and koi will get along with each other pretty well, but I have problem with the tropical fishes.

What is the guideline or rule for keeping tropical fishes? How do I know which one will get alone with the other pretty well? I read several sites and books about the good beginner fishes, I know those fishes are hardy and easy to take care, but a tiger barb wouldn’t fit well with a betta.

How do I know which fish will get alone with which fish? There are ton of tropical fishes out there, and I can’t make my choices.

I know my English isn’t that good, sorry. But can someone please answer my question.

Thank You.

[Captain Hook]

First of all I would get a bigger tank for your goldfish, especially if you also have koi. They get really big and should probably be in a minimum of 3x that tank.

Then I would use the 10 gallon you already have for tropical fish. In it you could put dwarf puffers (freshwater) by themselves. Or you could do a community tank, with small fish like platies, guppies, danios, tetras, cories, dwarf gouramies and ottos for algae.

[TKOS]

There is no simple rule for which fish go with which fish. I would suggest figuring which fish is the one you like the most, then find out what fish are compatible with it. That is the easiest way to go.

Also be aware that a 10 gallon tank will limit not only how many fish you can get but also what type. Don't be fooled by the size they are in the fish store as this is generally the baby version of many fish. Finding out all the info on the fish you like before you buy will save a lot of grief.

Oh and stay away from anything marked as Shark. They are catfish and generally get huge.

[aquariumfishguy]

Actually, in aquariums (esp smaller ones!) Koi and Goldfish do NOT get along. They fight for food, and will surely fight for space. They can actually slowly kill each other in this size aquarium...:(

Koi need about 100 gallons per fish as they can reach over 2 feet, despite what some people say about them assuming they require the same limits as goldfish. Goldfish, on the other hand get to around 1 foot full-grown and need about 20 gallons per fish. I should also mention that Koi can live near 100 years of age if cared for properly. Goldfish can live to 15-20 years easily...:)

If this seems unreasonable to you, its because you really dont have the money for this commitment and/or the time to invest into these fish --- which is also acceptable considering most dont realize these things until they already have the fish.

I am sorry I kind of drug this off track but I thought I would mention these things to you before you get too involved with other species of fish. I hope you can manage the room for these fish, if not hopefully you'll find someone who can better care for these fish.

[Cearbhaill]

Ditto on what aquariumfishguy said about the Goldfish/Koi.
They are wonderful and responsive animals who deserve proper space.

The only way to know what fish go with what other fish is to read, read, read. Then read some more. Books, websites, forums- Google is your friend.

And never forget- most any fish will eat any other fish that will fit in its mouth.

[Dahlia]

Also, remember you can always ask again on here when you have a set of fish you'd like to put together. Just try to decide which species you want and how many of each you would like, post it here with the size of tank you are considering, and people will be happy to advise you on it and make other suggestions.

Your checklist in trying to decide which fish fit together should include:

-Does the fish get too large for the tank?
-Is the tank overstocked? (The guideline for this is not concrete, but a good starting point is "One inch of small, thin torpedo-shaped fish per gallon or 1.5 to 2 inches of thicker fish per gallon." AND "Larger fish should be able to easily turn around in an aquarium, which means that fish that reach 7+ inches should have a 20 gallon tank minimum depending on the size of the fish.)
-Do the fish you want all prefer a similar range of temperature? Some tropical fish are best in the 72-78 F range and some prefer 79-85 F.
-Do your fish all prefer similar water chemistry? This would include pH, hardness/softness, and brackish conditions (some salt).
-Do your fish match in behavior? This is where you would watch out for putting nippy fish like tiger barbs with long finned, slow fish like bettas. You'd also need to watch out for very aggressive fish being put with peaceful ones, etc.
-Are any of your fish large enough to eat your other fish? I had a friend complain to me that angelfish were a "pain in the ***" because they ate his neons, and I pointed out this is their natural food in the wild. Watch out for giving your fish an expensive snack!
-Do your fish crowd each other? It is often good to consider the area of the tank your fish is expected to swim in. For example, a tank that had 3 corydoras (bottom area swimmers), a dwarf gourami (middle area swimmer), and 3-5 hatchetfish (top area swimmers) would give the fish plenty of room to themselves and you the pleasure of seeing fish in every area of your tank.

There are other things to consider, but this should put you on the right track.