Help! I've Inherited The Care Of A Piranha Tank.

I am a relatively new science department chair in a school that has two 200 gallon aquariums built into the wall of a classroom, visible to the hallway and classroom. Let me be clear, I have ZERO experience with fish. I like fish, but I haven't kept so much as a goldfish in my entire life. And I'm a physics teacher, so biological systems aren't at all my thing!

The lower tank contains two elderly piranhas. (Yes, they are legal in my state.) I do not know which species of piranha because, remember, I'm a physics teacher who owns cats, not a biologist who loves fish. I believe the fish are "elderly" because the teacher who previously cared for them for the last 15 years said they'd been in the tank when he was hired. He suspected they are original to the installation of the tank, which happened in 2000. He retired last year and I'm now in charge whether I like it or not. (And "not" is very much how I'm leaning.) I REALLY don't want to be the person who kills the fish that intrigued 19 graduating classes of students, at least not in the first month after inheriting responsibility for their care.

The previous caretaker obviously did something right to keep these fish alive for this long, but as I've been reading about the proper care of piranhas, I'm afraid the instructions he left me with are NOT standard for piranha care. They are fed pellets every other day, have conditioned water added to the tank monthly when evaporation drops the water levels considerably, and live in an aquarium with excellent filtration. There used to be a bottom feeder (don't ask me what species because I have no idea) but it died not long ago (and had no signs of ever being attacked by the piranhas. We think it just got old.) The piranhas are apparently healthy, as they are active but not aggressive and show no signs of disease.

Any advice about how to keep this aquarium healthy and clean would be much appreciated. None of what's been done for the last decade and a half seems like it's what's recommended to keep the fish healthy... Yet there's a very real chance that these fish are older than any of our students!

Thanks for any insight you can offer!

 

Hmm.. These fish have been healthy for the last decade and a half? Seems like the person who gave you instructions on their care would be the expert. If it were me, I would be strongly inclined to listen to him.

Don't forget that the internet "experts" you are referring to may be adolescents who aren't even as old as these fish!

I would note that "excellent filtration" probably refers to taking diligent care of the filter to make sure it doesn't get gunky, especially since there doesn't seem to be regular water changes - just topping off.
Just my two cents ... Curious to see what others say!
PS: Welcome to Fishlore!

 

Wow, what a predicament. I think maybe recruit a few responsible students and put together a weekly tank cleaning crew.
The tank needs a weekly 50% water change. You'll need a "Python Water Changer" and close access to a drain & faucet. The Python makes changing large volumes of water quick & easy. "Prime" water conditioner for the new water. Depending on what type of filtration, the filtering media will needs to be cleaned in "used tank water" every two or three
weeks. Continue the feeding program, its working.
This is just a very basic outline. Stay connected to the forum & ask questions as problems arise. Once you get into your tank maintenence routine, things won't seem so overwhelming. Hang in there.

 

Wow, what a predicament. I think maybe recruit a few responsible students and put together a weekly tank cleaning crew.
The tank needs a weekly 50% water change. You'll need a "Python Water Changer" and close access to a drain & faucet. The Python makes changing large volumes of water quick & easy. "Prime" water conditioner for the new water. Depending on what type of filtration, the filtering media will needs to be cleaned in "used tank water" every two or three
weeks. Continue the feeding program, its working.
This is just a very basic outline. Stay connected to the forum & ask questions as problems arise. Once you get into your tank maintenence routine, things won't seem so overwhelming. Hang in there.

Who will get to clean the algae off the inside - the good students or the bad?

 

If I found myself in your shoes I would follow the instructions left by their last caretaker. Changes could very well kill them since they seem to perfectly fine and healthy and not to mention elderly.

Don't try to fix what isn't broken.

 

Wow, what a predicament. I think maybe recruit a few responsible students and put together a weekly tank cleaning crew.
The tank needs a weekly 50% water change. You'll need a "Python Water Changer" and close access to a drain & faucet. The Python makes changing large volumes of water quick & easy. "Prime" water conditioner for the new water. Depending on what type of filtration, the filtering media will needs to be cleaned in "used tank water" every two or three
weeks. Continue the feeding program, its working.
This is just a very basic outline. Stay connected to the forum & ask questions as problems arise. Once you get into your tank maintenence routine, things won't seem so overwhelming. Hang in there.

The only problem I see with introducing water changes is that since they haven't been being done, do we not run the risk of upsetting the balance of the tank?

 

You didn't say, but I'm guessing your at a college/university. Even if it's a high school, there must be students that keep their own fish and if you put out the word to class and facility, I'm sure you will get some knowledgeable volunteers to help you out.

Good luck, and welcome to the forum

 

You told us the instructions told you what to feed them and how to top off the water. Do the instructions say anything about how to do maintenance on the filter?

 

Must be using purified water to top off the tank each month. 19 years of topping off the tank with regular tap water would likely lead to very dense & mineral rich water.

 

Must be using purified water to top off the tank each month. 19 years of topping off the tank with regular tap water would likely lead to very dense & mineral rich water.

How ever it has been done over the years apparently it is working and these fish seem to be acclimated to it. Changing the way the tank has been taken care of could very well kill them.

I am a firm believer in water changes but if they've not been done on these 2 tanks I couldn't in good conscious recommend starting now or doing anything different that what has been done so successfully.

Hopefully there were some very clear instructions given as to all aspects of taking care of these tanks/fish. Change sometimes leads to bad results.

 

Two Piranha, even fully grown, in a 200 gallon tank, don't need a massive 50% water change, but I would start 10-20% weekly. Also we don't know the setup of the tank. It may be built with an overflow/drain, so that when water is added, some water is removed. I set up my 125 that way, and believe me, it is very much easier than a water change with a hose, even a Python.

I've known people who kept the same Piranha for over 30 years. Don't know exactly how long they can live, but definitely a very long time.

I agree that finding students who are interested in fish would probably give you some help in maintaining the tank. Another alternative would be to hire an aquarium maintenance business to care for them. Of course, as a department head you would have to justify the expense, where students would likely work for free!

My curiosity would love for you to try and get a photo of the fish, just to see what species you do have. Keep in touch, let us know what you do and how it works out.

 

The place for information on these fish is monster fish keepers

Few people on here keep them.

The info vital to fishkeeping is understanding the nitrogen cycle.

Water quality is the main influencer of fish health.

I would not advocate wholesale changes but I would be expecting to change 25% of the tank water weekly for dechlorinated tap water and it would be important to add Prime or another water conditioner to the tank at this time.

I'd rinse the filter media in some removed tank water (not tapwater) only as often as is needed to prevent the filter becoming clogged. If the filter is full and the flow stops the fish may be in peril due to reduced water flow and reduced oxygenation. I rinse my filters monthly.

 

I agree with you mattgirl. Sudden change can be disaterous and your point is well taken. For convenience & ease in the transition, maintaining the status quo is logical and might be the proper way to go, at least in the short term.
Its a pretty safe bet that the current population of Piranhas won't make it another 19 years, and introducing new stock into the current environment might also be disaterous. Its important that the person entrusted with the huge responsibility of keeping such a massive tank know the basic fundamentals of aquarium water management.
IMO, although awsome fish, Piranhas make lousy aquarium fish, even in big tanks. Maybe the OP will eventually change things up.

 

I think that the OP's lack of knowledge about aquarium systems is leaving us without a lot of information that might change the way things sound. It's not their fault, obviously, but she definitely needs a somewhat experienced individual to look at it and figure out what's really going on. My money is on an overflow/drain, which would suggest that the "topping off" was actually a water change. That would give us an entirely different situation from the one most are assuming. Tanks built into walls are often plumbed for such a thing to make them easier to maintain.

As far as the current fish making it another 19 years, I wouldn't count it out.

 

Pictures of tank ,filter [hoses and all that jazz{we are fish nerds}] and the fish and you will have the 200 gallon piranha tank bible right here I would say !
You are in good hands with incredibly knowledgeable people already responding ..
Till you are told different do what was directed as mattgirl has mentioned ..Seems the most common sense approach so far. Hoping cd is right and you have some type of overflow /waste removal built in .. Most have not changed water on large tanks ..Even 25% of your tank is still 50gallons which is no joke and needs to be done properly ..My 180g lets me change 60 gallonin 5-7 minutes without ever touching water...
We need to know more about what products you have on hand like sea chem prime or what ever was left behind for you .
Welcome !