tiger barb compatibility

Question
Hi Nicole,

IK am a complete beginniner trying to give myself an aquarium crash course! I have the enviable job of stocking (but not maintaining daily care) of my daughter's large preschool aquarium. The teacher requested peaceful fish who will get along, but there are currently six tiger barbs and one lone molly (There had been six mollies but I think they did not like the too-low ph at one time.) I have been reading that the tiger barbs can be very nippy, but I'm confused as I read so much conflicting information about which fish are compatible with tiger barbs with regard to temperaments/ph requirements, etc. I was thinking about getting a bunch of platy's (cheap, colorful, hardier than mollies, I think) but I would like some more variety! This is a 125 gallon tank...I can't afford to completely fill it, but I would like an interesting, hardy, happy and varied group. What do you recommend?

Answer
Good morning Cynthia,

125 gallons, wow! That's neat that your daughter's preschool has invested in such a big aquarium. Big tanks have much more stable water quality, because the large volume of water means that changes to water quality happen gradually. A 10 gallon tank is much harder to maintain, because organics (from uneaten food and fish waste) foul the water rapidly.

The low pH indicates that this aquarium probably didn't receive any water changes for some time. Over time, aquariums do acidify if new water is not added. Top offs are very helpful but do not count towards water changes. The evaporation concentrates the earth elements in the water and top offs do little to dilute wastes. The good news is that if this tank is stocked lightly, one could get away with doing only about 10-15% water changes weekly.

See if you can talk the school into purchasing this: http://www.drsfostersmith.com/Product/Prod_Display.cfm?pcatid=3910
It really would make their life much simpler.

And now, the answer to your question! Platies are hardier than mollies, you are right, but they're still livebearers. They will reproduce and make more fish (maybe that's a good thing?) but they will still not be as tolerant of pH drops and declining water quality as say, a school of rosy barbs. The tiger barb aggression should be minimized since you have a fairly large school. If they are still acting nippy, it might help to add three more (odd numbered schools work best, in my experience) and observe to see what happens.

The best way to stock an aquarium is to evaluate the water chemistry right out of the tap and then stock accordingly. Community tanks prefer a pH of neutral, 7.0. That's because most fish are tolerant of neutral conditions, but some are INtolerant of higher or lower than neutral conditions.

Livebearers will prefer a higher pH with a high alkalinity, since this will "buffer" the pH and help keep it steady. If the pH is naturally below neutral (you live in an area of soft water) then I recommend you go with other barbs, who don't mind and even prefer these conditions. Rosy barbs, gold barbs, and other varities of tiger barbs (albino and green) will definitely add color and interest and are hardier than livebearers. It's tough to find a fish more colorful than a mature rosy barb, they even have "neon rosy barbs" which are more colorful still. You can see I'm a bit biased toward barbs, but I have found them very hardy.

Larger gouramis would certainly be able to fend off tiger barb aggression and would grow to be an impressive size without being enormous. Go to google.com and type in Trichogaster - this is the first part of the scientific name of many species of large gouramis. Avoid the dwarf gouramis, Colisa lalia. While very colorful, these are not hardy.

In general, I would prefer to steer you away from livebearers, unless you can be certain that the school is going to be performing regular water changes. They will react poorly to letting their water go stale. You can read more about livebearers here, if you are interested:
http://www.wetwebmedia.com/FWSubWebIndex/poeciliids.htm
Incidentally, if you do decide to go with livebearers, then platies or swordtails are going to be the way to go.

By the way, do you know what this tank has for filtration? I prefer canister filters for such large tanks, since the under the tank canister has plenty of room for biological media, which only needs a rinse in aquarium water (or tap water to which dechlorinator has been added). No need to ever replace anything. However canister filter units are expensive, so I'm placing my bets that the school has a hang-on back filter such as an Emperor. It looks like this:
http://www.marineland.com/products/consumer/con_emperor.asp

The only catch here, is that the regular filter cartridge replacements are expensive. *Someone* has to be responsible for changing them regularly - at least monthly, preferably twice a month. It would be much better to take out the cartridges and stuff the back of the filter with Poly Fill (craft store batting) and replace it weekly, than to leave a dirty filter cartridge sitting there forever. Batting costs maybe $2 a bag and lasts a long time, and while this isn't the ideal filter medium, it will mechanically remove waste.

I hope that I gave you some ideas. Please write back if you need clarification on anything or should you have another question(s). Also, thank you for writing!

Take care,
Nicole