A good quality heater like a Visitherm will never break unless you drop it on the floor. For 90 gal you will need two 300 watt heaters.

Yes they need a heater, they are tropicals. The Visi-therm "stealth" has a plastic casing and is very hard to break, like Raul said. I thought of using the "stealth" myself but I went with 2-300W Stainless Steel heaters by Via-aqua, they are unbreakable and the control is external so you don't have to stick your hand in the water to adjust the Temperature. The Via-Aqua stainless steel's where on sale from www.drsfostersmith.com, I got them during a sale, but even at full price they where a few bucks cheaper then the "stealth" by visi-therm. Via-Aqua are $20ea. for 300W and Visi-therm $21ea. They are good for big fish and aquariums with alot of rockwork. 2-300 watts is a good suggestion, so they don't get "over-worked" and die like yours. You could get away with 2-250W, I think it is 50W per 10 Gallons. Alot of people that have the larger tanks use a "sump" with a trickle filter and place the heater(s) in the sump so it's entirely out of the tank. Might be a consideration down the road, those Pacu get awfully big in no time for a 90G. They get big even for a lake. The extra water in the sump can be added to the total of your aquarium. The extra room for media will also help process the waste. Good Luck.

Thanks for the suggestions, I'll check into the Visitherm and Via Aqua types you mentioned. Nice to know they won't be too expensive either. You are right woeisme, the 2 pacu are 5 and 6 yrs old and have gotten very big. To think when we bought them they were about an inch!

The visitherm stealth is great... and what I've had to use for my cichlid tank (after going through 2 heaters and then coming across the stealth heater).

Hi
Would think you would need no more than 1 150 watt heater
to raise the water less than 10 degrees but won't argue the point lol. Do be sure and shop around anything with the word "Aquarium" in the title usually costs 3 times more lol.
gary

It depends on the volume of water. In a 90G a 150W would be overworked in the colder months. 1-300W is OK for a 90G but when the temperature falls it is easier for 2- to keep the water stable. Having 2 also allows you to place them at different heights or sides of the aquarium for more evenly heated water. Placing one by water flow is always a good idea. If you have to filters or sources of water flow then putting both by the output help. Always check the temp at the bottom as well as the top of the water line. Sometimes the bottom is too cold but the top is fine. Sometimes its a reverse bottom is fine the top is too hot. This happens more in bigger, deeper aquariums. Its thermo-layering, like when you put your hand in a pool and the water is comfortable feeling, then you jump in to find the bottom is freezing. The major cause of unwanted shrinkage.

Forgot to mention, over working an aquarium heater is risky. I would wager that most heater disasters are from over worked heaters. A good way to reduce heat loss and over work is a tight fitting glass top. The kind that are hinged and have a plastic strip on the back that can be trimmed tightly arround the filter returns, electric cords for pumps/heaters and airlines. The use of drill bits and rotary tools on the plastic strip will keep a nice neat, tight fit. Some air will always exchange a little.

The problem Gary is that a 150 watt heater is going to be overworked, besides that, it´s going to cost a fortune in electricity because it´s going to be running all the time.

Supposedly for 90 gals you should have a 300 watt and a 150 watt heater to keep the temperature stable but there´s not much a difference in price between a 150 watt and a 300 watt, I would rather spend a few extra bucks and get a 300 watt instead.

Hello
I use a 150 watt in a 75 gallon.Not only heats the water
actually warms the room. Yesterday for example , the outside air was 48 aquarium was 72 and the room 65.
I use a 300 watt on a 150 located outside .Will maintain 72 except when the temps fall below 40.I wrap the whole setup in bubblewrap when that happens. 3 sides are covered with styrofoam year around and styrofoam is also placed on top Also I cut external circulalation and step up internal..In my case I'm not to concerned with electrical consumption as the cold seldom lasts over 3 hours.
I'm in the process of joining the 150 to the 1000 gallon lily pool which is partly below ground. Going to try to maintain the whole thing at 70 year around and to keep the shadehouse frostproof. May end up using a spa heater though I think I'd be better off with several aquarium heaters.. Won't be finished until summer so have lots of time to think about it.
By the way , the only heater failure I've ever had is overheating. I'm using Ebo jaeger at the present time the 150 watt is almost 10 years old. The 300 has never experienced anything below 42 so far so don't really know what will happen.If we get one of those 27 degree nights
all bets are off lol
gary

the visitherm stealth is the way to go
i have it with my turtle and its pretty much indestructable

your tank is way over stocked im sorry to say. you wont be able to keep the 2 pacu's for long. they get enormous and fast! 24" + is not unusual
to house an udult pacu you would need a tank of at least 1800 gallons
ive read way too many times of owners having to kill their pacu's because no one would take them off their hands
some pet stores are stopping the sale of pacu's because most people buy them when they are small and cute and within a year they have a fish they cannot house properly.
pacu's suffer more abuse than any other aquarium fish

Thanks for all the suggestions here.
VaderBanger, the fish have all been in the same tank for a long time. We haven't added or taken anything away in 4yrs. The pacus are 7 and 8 yrs old. They grew rapidly at first, but seemed to stop after the first few years. They are big, but not nearly as large as those I've seen at public aquariums. I would never kill them. In fact, that's how we acquired the 2cd pacu, the owner said it was killing everything in his tank and we offered to take it, that was about 6 yrs ago and it was never aggressive in our tank.

pacu's arent aggressive. they are capable of eating smaller fish maybe that is what the person witnessed as "killing everything"
90 gallons is too small for what you have. an adult oscar needs 90 gallons to himself and this is without any other fish. it sounds like your pacu's are stunted due to the small tank, and yes 90 gallons is small considering the size and waste put out by these fish. any trace of amonia stunts a fishes growth, and high levels of nitrate weaken fish making them prone to disease.
a tank that crowded should have biweekly water changes of 30 percent.
do you check amonia and nitrate levels?
just curious how big are the pacu's? at the age you mentioned they should be at least 20 inches in length, if they arent then they are ill even if they are showing no signs yet

The older one is probably 17 in, the younger one maybe 15. We do small water changes every few days and a major cleaning and siphoning to remove waste once a month. They do generate alot of waste as you mentioned but the tank isn't dirty. I never even let it get to the point where the water starts to cloud. I don't check ammonia, nitrate, or any other levels regularly, the last time there was any sort of sickness in the tank was 4 yrs ago when they all got some kind of eye cloud. I agree with you pacus aren't aggressive at all, these 2 have never been. If something startles them they will move fast in the tank, I think that's how the heater got broken. I don't have any plans to get rid of them unless they become obviously ill, they sure don't seem to be now with as much as they like to eat and swim, but I would find a new owner for them if this ever happened.

a 17 inch fish in a tank that is only 48" long is cruelty, i know you love them but step back and look at the tank, you must be able to tell that its cramped? and that it doesnt look normal.
its very hard to find a home for a near full grown pacu, its basically impossible. this is why people usually end up euthinizing them.
at that size if panicked enough they can even break the glass.
to lighten the load it would be easier to get rid of or move the other fish to another aquarium so the pacu's can have "some" breathing room
a larger custom made tank is really expensive, another option in warmer climates are ponds for pacu's. they do great in ponds where the temps dont get too low.
i wish your little guys or shall i say big guys the best
let this be a lesson to anyone wanting a pacu, dont get them unless you can accomadate them

I would go with All-Glass Heaters. They make high quality heaters and even fish tanks. Very high quality brand...own several things of theirs.
Its what i have, and i've never had any problems with it

I would just like to add for anyone reading this post, that I highly recommend Aquarium Systems Vis-Therm heaters. I have a 100W Visi-Therm that I purchased in 1988 and this heater is still in use today in my 10gal tank. I just recently ordered a Visi-Therm Stealth that I plan on using in a new 20gal setup. I will be passing the 10gal on to my son along with the always reliable Visi-Therm heater. I hope the new Stealth lives up to the quality and dependability of the original Visi-Therm.

You wrote that your heater was broken LAST YEAR.

But then you write that the fish are doing fine without it.

Aquarium heaters are necessary when the ambient air in the room is too cold for the fish, but if your home maintains a fairly steady temp that apparently suits the fish- why bother with a heater at all?

BTW: I'm sorry, but I must agree with those who wrote about oversized fish in undersized tanks. In their native habitat, like their toothy cousins, Pacu are food fish except that unlike most Piranha, even when filleted, a single full grown Pacu will feed an entire family.