How Many Fish can i put in my 20 gallon tank? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 5 Old 06-16-2009, 10:56 AM Thread Starter
Smile How Many Fish can i put in my 20 gallon tank?

Hey, Ive had fish now for about 3 or 4 months, and every week I get 2 or 3 fish or I get a new plant. So now I have 10 fish; 2 mollies, 2 platys, 2 bloodfin tetras, 1 algae eater, 1 swordtail and 2 guppies. Can I add anymore fish?
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post #2 of 5 Old 06-16-2009, 12:12 PM
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figure out the adult size of each of your fish. The rule is 1" per gallon of water. That way you will not be overstocked with fish. Understocking is better then overstocking. You should add a bottom feeder in your tank like a small Cory cat or 2. Bushy nosed plecos do an excellent job on cleaning algae better then an algae eater. I hope you got one that does not get really large as some algae eaters can grow quite big. BN plecos only get about 4-4 1/2 inches but I had a adult female that only got to be 3" full grown. If you want 1 big fish in that tank get a baby angelfish as they grow up with the fish you have and will get along with them if bought as a baby or baby dwarf Gouarmi keep in mind that an angelfish will get to be about 6" full grown, dwarf gouarmi about 3". They will keep your livebearer population down in your tank so it does not get out of hand. Take all of your full grown size and total it. It should not be over 20". If you go alittle over it would be ok as long as you do 25% water change a week and use a product like Cycle or Easy Balance to maintain good water parameters and do weekly tests on your water with a dropper test kit for PH, Ammonia, Nitrate, Nitrate. You should be good then.
Dont' add fish to soon when getting new fish to a newly cycled tank wait a month or 2 in between adding fish. Live plants will also make a differance in your water quality.If you want a good community tank have floating plants for baby frys and taller plants for cover for the other fish. If you go with a small school of tetras make sure you get a small group of them like 5 or more.
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post #3 of 5 Old 06-17-2009, 01:45 AM
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I can't say that I agree with all of that advice.

For one, the inch-per-gallon rule isn't really even all that useful as an "estimate" for stocking purposes. Different fish simply have different needs. You need to take into account bioload, territoriality, preferred swimming levels, schooling, swimming speed, compatibility with other fish, etc.

That said: is your tank a 20g long or a 20 high? A 20 long is 30" long but is lower, a 20 high is 24" long but higher.

The livebearers that you already have are generally alright in small groups or even alone, so schooling isn't really a concern for them. The bloodfin tetras, on the other hand, are schooling fish so I would recommend getting four more of them to increase your school size to six.

What type of fish is your "algae eater"? The two most common fish sold as such are Chinese algae eaters and common plecos, both of which are unsuitable for your tank. The common pleco grows to 18", produces a ton of waste, and doesn't eat much algae when it gets bigger. Chinese algae eaters don't really eat algae at all, grow to 6" and become very aggressive as they grow. They are known to terrorize, kill and eat friendlier tankmates. Although no fish should be relied on for algae control, a better choice would be the bristlenose pleco that eileen suggested as they stay smaller and do a much better job of eating algae.

An angelfish will get much too large for a 20g tank. I also wouldn't add any gouramis since you have so many livebearers that already inhabit the upper areas of your tank.

So, I would recommend replacing your "algae eater" with a more suitable fish and increasing the school size of your bloodfin tetras and you'd end up with a well-stocked tank.

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post #4 of 5 Old 06-18-2009, 08:47 AM Thread Starter
Thank You SO much, but I do have a few more questions:
1. I bought my albino chinese algae eater and my local petstore said that it would only grow to about 4 inches, was that a lie?
2. How long do I have untill he will get aggresive?
3. What should I do with him? I have already grown to love him, but I will not keep him if he will end up hurting my guppies (because I love them way more than i love the algae eater).
Thank You eileen and iamntbatman for your very helpful responses.
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post #5 of 5 Old 06-18-2009, 11:20 AM
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1. I'm not entirely sure if that's a lie since in some fishes, albinos tend to be a little smaller than normal-colored
2. How big is it now? Probably it'll be agressive when it reaches adult size or near it.
3. You can return him to the petshop. I don't know what setups can accomodate this kind of fish, but if you find someone who is willing to take it in, then lucky you. As a last option, you can euthanize the fish. I believe it's better to euthanize than to release into the wild, since it might upset the ecosystem or die an even more horrible death. But remember, only euthanize as a last resort.

Your fish love watching you as much as you love watching them. So please practice responsible fishkeeping.

Last edited by adiumroot; 06-18-2009 at 11:25 AM.
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