Tropical Fish Keeping - Aquarium fish care and resources

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love_my_fish 12-02-2006 11:39 AM

Undergravel heater
I've read books in the past that suggest using a heater under your gravel, or under your tank if keeping plants.


Andrew 12-02-2006 03:54 PM

its supposed to help by providing a uniform heat in the substrate, this will also aid the uptake of nutrients.
I didnt do it. but if i were to strip my tank down i would.
It also means that you wont have to have an unsightly heater in your tank!

crazie.eddie 12-02-2006 04:00 PM

I don't know of anyone with heavily planted tanks using them in the US. If you don't want to see a heater, use an inline heater, which connects to the output tubes of your canister filter.

caferacermike 12-03-2006 12:05 AM

Eddie now you do.

We run a Duplamat 150 in our 20g. The theory being that it keeps the substrate warm. Warm air and water seem to rise. This creates a convection through the substrate. As the warm water leaves the cool water replaces it, thus flushing the roots with nutrients. Can't say for sure if it helps or not due to lack of trying it any other way. My LFS (which has several awesome plant tanks) swears by them. If you look under the stands you'll see giant root masses.

crazie.eddie 12-03-2006 12:12 AM


They're are not just that popular from the many planted tank forums I belong to. As far as the benefits, I know many of them have BEAUTIFUL planted tanks using glass heaters or in-line heaters.

As far as getting nutrients for the plants, most of it is just achieved through the water column. A good current is all that's needed. If you notice when you pour liquid nutrients in the water, it sinks then spreads around the tank via the current. I guess you wouldn't want the nutrients to be pushed upward.

From the look of Andrews sig, he has a beautiful planted tank and not even using heating cables.

crazie.eddie 12-03-2006 11:57 AM

I asked a question on one of the planted tank forums I belong to regarding their use and here is one of the replies I received...


Originally Posted by frozenoak
I have them. There only real advantage is that they are hidden. The only thing you see is the cord that runs from the top of the tank to the gravel. That is easier to hide than the larger traditional heater.

I don't think there is a large advantage otherwise. It is theorized that the gentle heat coming from below the roots would help imitate the natural environment that aquatic plants thrive in, but I have doubts about this. At least in southern California where it rarely gets cold enough for the heater to be needed.

The big disadvantage, if you like to change your plants, would be that the plant roots entangle the cord. If you pull one plant it will most likely bring the cord with it. Now you have a cord above the gravel and it is a pain to get it buried again and any plants that were close by are probably half uprooted also.

In conclusion. If you are concerned about the ability to hide your hardware and you don't plan on changing anything around undergravel heaters might be your ticket. If I had it to do allover again I would go with the in-line heater or the canister filter with the built in heater by Eheim..

Hope this helped,

Aquaticmoon 12-03-2006 12:05 PM

Imo they are not worth the money in a planted tank for the same reasons pointed out by eddie.

love_my_fish 12-03-2006 12:14 PM

Thanks for your thoughts -- I havent' really seen any in the lfs, and wondered if there was any real advantage. There is definately a temp difference in the water above the gravel and below, but wasn't sure how much that affects the plants themselves.

crazie.eddie 12-03-2006 12:30 PM

Plants are not that sensitive to temp differences. I've tossed plants from my heated tanks 82°F (28°C) into a 5.5 gallon unheated tank (I would assume about 72°F) with only a filter and a desk lamp and they are still surviving. I dare not do that with any fish.

Andrew 12-07-2006 04:51 PM

well of course it makes a difference, current or not you are not going to get uniform heat any other way, have you noticed the temperature of the water 3/4 down, and how the water is cool in the thick of plants???
Undergravel heat is a way of ensuring a balance heat for plants, a heater inline or in the tank wont provide the same temp balance for every tank. They can be used to great effect with carpet o=plants, there is nothing to suggest you can carpet without it, but you will see quicker more positive results with this method. As for the inline method, this is an expensive heater to run, and quite wasteful, quite green here in the uk, so will stick to intank heaters.

The only draw back i can think of undergravel heaters in the delay between heating the substrate and the temperature probe reading in the body of water, the delay might give rise to temp fluctuations until you have the settings down.

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