I have have a 35 gal tank, i was wondering if anyone had any good ideas on what fish to add or if i have enough already. I have 6 tiger barbs, 4 giant danios, 1 rainbow shark, 1 dragon goby, and 1 common pleco(I already know that it will out grow my tank i have a friend who is willing to take it when he gets to big). All my fish are still pretty young i have only had my tank 2 months. I want something different to put in but it will have to be atleast semi-agressive b/c all my other fish are semi- agreesive right?

it doesnt nessacarily have to be but it would be a good idea to have something to defend itself. Also im not sure about your tank dimensions from what i under stand sharks are active and need at least 4ft of tank... also i know for a fact that dragon gobies are brackish water fish which means if you dont remove it, it probably not going to do so well and also needs 4ft of tank. this is just my understanding to the best of my knowledge thou.

The goby is also a filter feeder (Despite what the stores around here advertise, it'll only eat feeder fish if it's near starving), so it may be tough to feed if you're following store advice. I researched them a few months ago, and supposedly they can be acclimated to fresh water with some disease risk but shortened life (i.e. bad idea), and can be acclimated to fully marine conditions over a period of weeks. They're very adaptable to water conditions and have been known to be the sole survivors of tank-clearing disasters. Here's the most complete info I found in my research. I shudder to think how much damage 75 ppm of nitrite or the ammonia required to produce it would do to any fish, even one able to survive in it.

To address your other questions, you've got a good group of barbs, so I don't think they'll bother most fish. You don't neccessarily need semi-aggressive fish (some semi-aggressive fish should be kept with peaceful tankmates, for that matter), but avoid anything with long fins which the barbs likely won't be able to resist, and likely stick to fast moving fish of a comparable size - the danios should be good, maybe black widow or serpae tetras.

The goby probably won't last in the long term unless you can find a brackish tank to rehome him. Since you have a plan to rehome the pleco, you can consider doing so sooner instead of later, and replacing him with a bristlenose, which is a very similar fish and more suitable to the tank size. I don't know much with rainbow sharks, but Alex is saying much like what I've heard in the past. Watch him for aggression, as they claim large territories, and don't add another shark (even a different species) to the tank, or they'll likely terrorize each other.

This post has been edited by Corleone: Jun 12 2008, 11:37 PM

Thanks for the advice, I should have been more specific i am looking for something that would be a bottom dweller but not need to have company of its own kind b/c i don't think there will be room when they all get big. My tank is only 3 feet do u think the shark will be alright in that? If he does get aggressive won't it be ok since all my other fish are aggressive as well? As for the dragon goby my friend has had 2 in his freshwater tank for about a year now, both look fine and are at least 12in probable more. All he does is put some aquarium salt in the tank. I know he is a filter feed, i feed him shrimp pellets and when i put them in the tank he instantly comes out of his cave and goes crazy. Of course he also comes out at night too and sifts through the rocks. Do u think he has just go lucky or is this fine? I have read about people doing that online too. I want a bristle nose but can't find any right know the guy at petsmart said that there has to be some problem b/c they haven't had them in a few months, but if i get 1 that common pleco is gone.

Well, as I said, they can be kept in fresh water if acclimated, and they're usually sold out of fresh water to start with, so it's more a matter of acclimating them to brackish conditions. Just keep in mind they will live over ten years in good conditions - in general, unless I know of somebody who's kept a fish in different conditions for half of its lifespan, I don't assume it can be sustained. They're hardy gobies if they can survive the extremes of bad water I've read about, but there's a huge gap between surviving and thriving.

As for the shark, 3 feet is the minimum for them, so you're ok there. Rainbow sharks are E. frenatus, I think, and E. bicolor are the more aggressive species. Don't get any other sharks, and watch him for aggression towards tankmates.

PetSmart's semi-aggressive and community classifications are mostly bunk. Ignoring the number of semi-aggressive species they list as community and vice-versa, there's a lot of compatibility across their categories, and even more incompatibility inside their semi-aggressive category. Just because a fish is semi-aggressive doesn't mean they should be kept with other such fish - an angelfish in your tank (which PetSmart's information says is an ideal tankmate) would might become a victim of harassment from the tiger barbs, which are notorious fin nippers.