DaveH

I was just at the petstore with intentions to get a redtail shark. there was a tank full of all rainbows and no redtails, so i was talked into getting a rainbow instead. I came on the site to check it out under the impression that "it is almost the same fish, except all of its fins are red instead of just the tail."
Upon reading some information, i see that a 55gal tank is suggested for a rainbow shark whereas only a 10gal is suggested for a redtail, this leads me to believe that the rainbow shark is much more aggressive, seeing as they grow to the same size.
are rainbow sharks generally more aggressive than redtails?

6 tiger barbs, 3 cory cats, 1 pleco, 1 rainbow shark. 20gal tank.

susitna-flower

You already have your 20 gallon tank overcrowded!

Is the pleco a common? That can grow huge!

The rule of thumb for stocking a tank is 1" of adult size per gallon of tank.

This is why in the articles for beginners setting up a tank it gives proper stocking limits....You should research before you even buy a tank. This way you have an idea before you go to the store and fall in love with a fish, just to find out there will be problems later on. THE START OF MTS IS ...........

So now you have a decision to make. Depending on what pleco you have, you already have enough fish for between 45 and 75 gallon tank. I say this based on it being a bristlenose, or a common pleco. The common grows large, but its size is not even the only factor. They are huge waste producers, and need room to move around. I've had them in a 55 gallon tank, and they just don't fit!

Two suggestions on stocking. TAKE the shark and pleco back (if it is a common pleco), and pick up EITHER 3 otoes, or a bristlenose pleco. This will still be overcrowded, but manageable. Just make more frequent water changes.

Do you have an API Master test kit to check your water chemistry? We recommend this kit as it has all necessary tests, and will do hundreds of tests. You should test every day till your cycle is finished, then once a week at least, to make sure your tank is safe. This will also help you know before fish get sick from water conditions, so you know just how often the water changes are necessary. If you have the test kit, what are the readings for:
Ammonia?
Nitrite?
Nitrate?
Temperature?
PH is nice to know, but don't mess with it, MOST fish can accommodate to your ph much better than they can stand ups and downs caused by your trying to change it to their "ideal" range.

Hope this helps, sorry for the news. I just want to help you keep your tank healthy.....

KittieKat

rainbows and red tails dont grow to the same length! rainbows can get to 6-7" and red tails can get 3-4"... there really is a difference!!

oneidkat

Aggressiveness can be cause by having your fish in water of the wrong ph level. As sustina-flower said, you really should be checking the ph level and avoiding swinging extremes.