w Neon Rainbowfish - Melanotaenia praecox
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Melanotaenia praecox
Neon Rainbowfish

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praecox2.jpg (8kb)
Photo Credit: Shawna

Name: Melanotaenia praecox
Origin: New Guinea

Size Tank pH Temp
6 cm 60 L 7.0 26C


This is an active, beautiful and hardy fish - of the half dozen I bought a year ago, five are still doing well (the one that didn't was a little too aggressive chasing fish flakes on the surface and actually leapt out of my tank!). Males are smaller and narrower and have more of the silvery bluish tinge in their bodies and more orange in their fins. The females are larger and have more yellow in their fins.

This is my favorite fish to watch in my tank (a 70 gallon community w/ a handful of corys, rasboras, a gourami and a flying fox) - and fast studies in food acquisition. They do extremely well with the other fish, but the five I have left have gotten adept at catching with their mouths whole shrimp pellets intended for the corys, holding the pellet in their mouth (even though it's too large for them to swallow) and letting the pellet soften in the water before attempting to eat them whole. Sometimes they'll chase each other around trying to force the chasee to drop its pellet; the smart ones have learned to get the pellet and go hide long enough for it to dissolve so that it can close its mouth over it. They've also learned to hang around the corys and the flying fox at feeding time, figuring that one of them will dig up a stray pellet remnants for them to try and eat. Sometimes the flying fox will chase them in what I swear appears to be an act of frustration!

When they're not trying to figure out how to swipe food from each other, the Praecox likes to school loosely and I'd recommend keeping them in at least groups of five to seven. Soft, alkaline water (an unusual combo, but that's what comes out of my taps) and 75 F temperature seems to suit them just fine. It is a good looking fish and among the more interesting to watch!

Contributed by Dan Shim

I have 4 of these fish. I've noticed that the 2 females school together, and the males hang out by themselves without schooling. One of the females is a juvenile, and she's growing MUCH faster than the 2 juvenile males I bought on the same day! She's almost as large as my adult female! I've also noticed that the females are the bosses of the bunch. They chase the males away & keep them in their own little corners of the tank while they (the females) swim freely wherever they like. They're easy to feed, and readily take flake and live or frozen brine shrimp. They also like to nibble on the spirulina disks I toss in occasionally. If a spider or other insect happens to fall into the tank, these fish are ALL over it! SNIP SNAP GONE! A very gorgeous fish, the colors don't really shine until the fish reaches maturity. When they're young, they have very little color, but are still attractive.

Contributed by Shawna McGregor-King

I have kept four neon rainbows (2 males, 2 females, I think) for over the past two years in a 75 L tank and they are doing great...just changed their water . Initially, I was treating the tap water i.e., keeping it around 6.5-6.8 pH, etc, but eventually I weaned them away from this chemical "water massaging" and into using the tap water straight out of the faucet - treated for chlorine and aged in an 20 L plastic container, of course! If you're limited on space, I can't tout these little ones enough! Also, they're tough fish and don't have to be pampered like a discus. But still - as with all fish - I would prescribe good tank maintenance to keep them happy. And despite the temptation, don't overcrowd!

Contributed by (no name given)

I find keeping them in a big school the best way to keep them but this also means larger tanks are more suitable for this fish - 100 liters and above. I regulary do a 20% water change (daily if I have the time) without even adding anti-chlorine and they seem to cope very well with it. I feed them TetraBits and they still spawn with just this diet. But I must add that I keep them in full sun conditions and in a heavily planted tank with only a weak airstone (I live in the tropics so I do not need heaters) and the tank does contain some water fleas and other stuff I cannot see. They love frozen bloodworms, it's good but overfeeding may result in them having the same intestinal problems like discus, so be forewarned. I have stopped feeding them frozen bloodworms for I find it is very difficult to treat them once they get it even with tons of metronidazol antibiotics. So far, I find them to be quite sensitive to sudden water changes, for I have lost quite a few when I tried moving them from tank to tank. Furthermore, in my opinion, rainbowfish is quite hard to treat when sick and when they want to die, they will just die on you without warning.

Contributed by Edvin Ong

I have kept a school of these stunning fish for over 2 years now, and they are always of great entertainment value. I have only recently added a couple of females to the tank and this has caused some considerable aggression between the males.

Contributed by John Walsh

I have four juvenile praecox in my 100 L community tank with platies, cories, a bristlenose pleco, and a dwarf gourami. The other fish seemed overwhelmed at first by the rainbow's frenzied feeding behavior, but they adjusted. I have three females and a male, but I remember reading that a school of all males is more colorful, because they display to each other. They seem happy in my very hard water and at pH 8.0, and they enjoy flake, bloodworms, and brine shrimp. I recommend praecox rainbows to anyone with a smaller sized peaceful community tank, because they are gorgeous, hardy (in my experience), not as large as other rainbowfish species, and they don't have any special requirements. A good fish for beginners!

Contributed by Martha Mullins

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