Tank getting too Hot…

ShawnSaucier · Apr 30, 2026

So I have been having issues with heat in my system for the last couple of months. 82.3 was the top so far.
I have narrowed it down to my UV reactor. This I took off line yesterday as a test. Tank has dropped almost 3 degrees since noon yesterday. So far. I am going to keep this off line for the weekend and see how much difference we get.
I have a 25w Aqua Vita unit that I have had for at least 10 years. Bulb and sleeve routinely changed yearly and last done in Sept.
This kinda has me in a mental pickle as I have been a big fan of having UV on my systems for perceived prevention. I have rarely had ich issues, only on a few fish ( new additions) over the years but always remedied, And the same with algae ( cyano or dinos). Now I am down a possible safety net that I have always relied on.
In this system I have a separate pump ( Varios 8 running at 50%) feeding my manifold, so two pumps in the return chamber. I might drop down to an Ecotech S2 or M2 as my plumbing is all 1” not 1.25 like the output on the V-8. But not sure this is going to fix this problem.
Are there better UV units that handle heat dispersion better?
Any suggestions welcomed.

W31Olds · Apr 30, 2026

I have an 80 Watt unit on my Tank and it will heat up the water a degree or two. This is one of the pitfalls of running a UV System. They all basically use the same design to Sterilize Water so I doubt changing your unit would help. I would experiment with a small fan or two exchanging air in the Sump and over the Tank. I run a Chiller but that gets expensive for the Unit and adds to your Energy Bill.

mfinn · Apr 30, 2026

If this were me and I wanted to run uv on my system, I would try adding a small clip-on fan to blow air at the uv unit.

ShawnSaucier · Apr 30, 2026

W31Olds said:
I have an 80 Watt unit on my Tank and it will heat up the water a degree or two. This is one of the pitfalls of running a UV System. They all basically use the same design to Sterilize Water so I doubt changing your unit would help. I would experiment with a small fan or two exchanging air in the Sump and over the Tank. I run a Chiller but that gets expensive for the Unit and adds to your Energy Bill.

If a chiller was an option, it would be my go too for sure. Unfortunately not in the current setting.
I’m waiting to see where the tank temp stabilizes over the next couple of days, then I will bring the manifold pump back online without running the UV and see where that settles to. This should give me an idea if it’s a multi point equipment change/addition. If that doesn’t cause a spike, then I will have an idea on what the UV is doing temp wise, theoretically.
The tank is in the down draft of an AC vent, but not directly. And the ambient temp in the house is between 72-78 degrees depending on the time of year.
Fans are a viable option as well. Not sure how much my netted lid would interfere.

X-37B · Apr 30, 2026

On my 150, 60×30×21, I run a Tunze aquawind. Room can get to 82 and tank stays 78, set at 77.
It sits on the euro brace at one end and blows across the surface.
The top is covered with a mesh lid.
I also run one on my 112 halide system running in the same room With no lid yet.

mfinn · Apr 30, 2026

ShawnSaucier said:
If a chiller was an option, it would be my go too for sure. Unfortunately not in the current setting.
I’m waiting to see where the tank temp stabilizes over the next couple of days, then I will bring the manifold pump back online without running the UV and see where that settles to. This should give me an idea if it’s a multi point equipment change/addition. If that doesn’t cause a spike, then I will have an idea on what the UV is doing temp wise, theoretically.
The tank is in the down draft of an AC vent, but not directly. And the ambient temp in the house is between 72-78 degrees depending on the time of year.
Fans are a viable option as well. Not sure how much my netted lid would interfere.

Once the temp stabilizes, turn it back on with just a fan on the uv unit and see if it takes care of the issue.
May not need more fans.

Privateye · Apr 30, 2026

UV sterilizers dissipate heat by putting it into the water, so there isn't a great way to dissipate it through other means.

The type of UV lamp can affect the heat output though. A standard output, low-pressure T5 won't put out much heat. I left two 40W Pentair UVs on with no water flow for 2 weeks by accident, and they were fine.

High output T5s put out more heat, but usually offer a more-compact package for a stronger lamp.

Amalgam lamps put out a good amount of heat. If you leave the unit on without flow, expect seals to fail.

Medium pressure lamps put out a ton of heat too.

If your tank does fine without the UV then that sounds fine to me. If it doesn't, I'd adjust my air conditioning. I don't really want to mess with chillers either.