5 Gallon Tank Nicrew heater failure and tear down

  • #1
Edit: teardown pictures in reply!

HI guys, it's me; your friendly neighborhood nicrew fanboy. Today I sadly had a nicrew fanboy level -150 incident when I had a heater I have recommended here go bad.
It was this one:
Which is allot like this one:

And on Amazon it looks like this:
NICREW MinI Preset Aquarium Heater, 25W Submersible Betta Fish Tank Heater with Electronic Thermostat Amazon.com: NICREW MinI Preset Aquarium Heater, 25W Submersible Betta Fish Tank Heater with Electronic Thermostat: Pet Supplies

Notice the recent reviews from this month..

There is a difference in their heaters that I use, I have 3 of the 15 watt, 2 currently running, one in box spare. I *had* one 25 watt.

The 25 watt was in a 5 gallon round, that I had put this generations endler guppy mutt fry in prior to the company coming for the holidays. I have been trying to tidy up my fish room and take the hobby a little more seriously since I'm no longer colony/mass breeding to feed a small reptile(he has moved on to worms and calcium supplements).

These heaters have a design flaw I have known about for quite a while, they have an internal mechanical float switch that gets stuck and the heater won't turn back on after a waterchange. If you rinse the heater off during your cleaning routine this is not a problem. I have always unplugged my heaters before changing water, and was not bothered by this.

My oldest 15 watt heater by them has been running since last May, and keeps that shallow tank in the second picture (snake pond/momma guppies) perfectly. The tank is very shallow, houses all breeds of baby snail, guppy fry and a semI aquatic snake so I needed one that didn't get burning hot to the touch, had no silly jagged cut outs, was not glass or fragile and could operate in just 6 inches of water/~4.5 gallons. The snake regularly beats the heck out of it and used it to climb on and it has had no issues. Despite a huge surface area (vs total volume)and mesh top on that tank I haven't needed a bigger heater as the tank also has a under tank heater on the dry side.

About 2 months ago it was coming time for my 4th generation of guppy fry to drop. I usually fully separate and grow them out between generations so I have a surge period of about 3 months on and 3 months off where I need multiple small bodies of water. My wife has kindly let me turn our family/sitting room into a fish room/reading room and asked that I not keep a bunch of Tupperware tubs scattered about, it was the least I could do. I pulled out some retired betta tanks and made them "pretty" (it's temporary). I needed another heater for the biggest one so I ordered another nicrew (the 15 watt spare is for the snake tank. Period. It was hard to find one I liked so it's sitting in the box forever). The only nicrew nano heater available at the time was the 25 watt of the same form factor. This was my mistake.

The 25 watt clearly should not have been the same form factor. Today I came in from building some shelves in my shed and noticed the female juvie tank was about 85 degrees. I unplugged and replugged the heater and noticed the led was not on, or flashing so I pulled it out. When I opened the lid you could smell a compound similar to chlorine. I tossed the heater in a pitcher of warm water and changed the water out in the baby tank. I put all the females in a specimen tank, while I washed the 5 gallon, I tossed the marbles in the dishwasher and loaded the tank up with some sand and rocks I had pulled from the snake tank. I pulled the sponge filter apart and washed the plastic, and gave the sponge a few too many squeezes so I have now (hopefully) reseeded it, but will seed again tomorrow after parameter testing.

Being a nerd, I decided I would run the heater in a pitcher of water while I ran to the lfs and bought the only 20 watt heater with a real switching thermostat in it they had, it's the topfin betta heater, hopefully it runs for a while longer than the nicrew 25 watt did. About an hour into the testing in the pitcher, all the magic smoke did indeed come out of the nicrew, it was awful. Black water, smelled like electricity in a fireworks stand.

Tomorrow, if I get a minute I will put the heater on the electronics bench at work and see what I can see. Sadly I didn't think to take a picture of the nasty black water in the pitcher to share with you. I'll post any findings for the nerds among us.

I can now say, please, do not buy that heater I recommended. I will be continuing the search for a good small form factor heater, and hope that the 15 watt units do not fail while I am away from home. So far, none of my undetermined, or female fry/juvies have passed but I would not be surprised if there are issues down the road from whatever chemical that gave the chlorine odor.

I still do like the light by nicrew I have used, but the heaters may be further dismantled for science...

  • #2
Thanks for the heads up

  • Thread Starter
  • #3
For the nerds:
When your rework station is worth more than 300X the item you want to investigate:

First I removed the cap. The old float switch I have noticed in the 15 watt version is absent.

There is a resistive water sensor detector in place it appears as the black circle. The side with the black circle contains a control pcb. The other side contains a simple 25 watt wirewound ceramic resistor(used to make heat).


This spring is an inductive thermostat.


In this case, the damage was not in fact in the heater section, but a currently unknown module on the PCB. I would assume there should have been a very small rectifier at that location as that is where the (115vAC) power comes in, but the circuits exposed would run on 5-12vDC. There may have been a mossfet in that location as well depending on how they choose to drive power to the resistor.

Unfortunately the damage was too far spread on the PCB for me to connect it to any analyzers, or identify several of the parts due to discoloration/delamination.

Anyhow. Don't buy the 25 W nicrew heater.


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  • #4
Wow. Impressive soldering station you have !

Ive got an old school car amplifier I need to send you that needs a part replaced on the board, LOL !
  • Thread Starter
  • #5
Wow. Impressive soldering station you have !

Ive got an old school car amplifier I need to send you that needs a part replaced on the board, LOL !
Funniest part was how little of the rework station I actually used. I was expecting to find a resin in there and have to use several of the more advanced pieces of kit. When I opened it up and found cast rubber I almost laughed.

I've done a few old school amps. If I'm ever down your way I'll swing by and do it with my portable kit, don't toss that thing, it's getting hard to find good class a/b and even c anymore. I can see the difference with the digitals on my scopes, and can even hear it in the right environment. Those digitals really can keep a speakers coils cooler down in the 40-60 hz range though.
  • #6
Interesting about the digital amps. I've got some old gear stashed and not being used.

The amp I referred to is a Kicker ZR240, their last series of amps still made in America. Probably around 21 years old. .

I've found it strange that old school fish keeping gear is not really something that's seen. Maybe the occasional old Oceanic tank, but that's about it.

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