An argument settled at last

Before my recent business trip to Europe, I did some experiments with substrate heating coils. Since I was going to have plenty of free time on the airplane on the flights to and from Brussels, I took along my notes and wrote up the results on my laptop. The results were so intriquing that I had to post this right away, even though I just got off the plane a few hours ago.

George Booth
Ft. Collins, Colorado

Conclusive Proof: Substrate Heating Coils Really Work!


Various things recently have provided the opportunity and impetus to dive into substrate heating coil experiments.

(1) There has been a plethora of disparaging remarks from certain APD-ites about the lack of scientific evidence that heating coils do anything more than waste electricity. The gods of Dupla apparently don't care to toss their 2 centi-EUs into the fray so I've been challanged to present some evidence of my own.

(2) We have an old 29 gallon tank that used to be a quarantine and hospital tank.  We haven't bought any new fish lately and we don't really believe in treating sick fish with all the patent medicines available, so the tank hasn't used for awhile. I decided to set it up as a heating coil experiment and try to refute or verify some of the conjecture that has been bantered about recently.

(3) Some time ago, Karla was telling me about one of her biochemistry procedures called "sodium dodecyl sulphate Polyacrylamide Gel Electrophoresis" or SDS-PAGE for short. As best as I could interpret, electrophoresis is used to determine relative molecular weights of enzymes and proteins by putting them on a plate covered with gel and applying an electric field. After a time, compounds with different molecular weights will have migrated different distances across the plate and you can tell what they may be.  Anyway, that conversation planted the seed of "electric fields and organic things" in my head somewhere.

(4) Recently, while going through piles of old fish magazines, I came across an ad for a device that supposedly uses electric fields or currents to denitrify water.  Although my cynical inner-self had me rolling on the floor in laughter, another random thought was planted the murky backwaters of my brain.


Before I go further, I would like to state that what I am describing could have the potential for danger.  Keep in mind that water and electricity are a deadly combination and should not be trifled with. I am a qualified electrical engineer and have taken appropriate precautions with the setup I'm going to describe. I would strongly dissuade any one from trying to dulpacate this until more information is discovered about the processes involved.


The stated purpose of substrate heating coils is to create slow convection currents that bring nutrients such as NH4++, Fe++, Ca++, Mg++, etc. into the root zone for eventual adsorption by the plant roots.  Besides the water currents that keep the substrate rich with nutrients, the coils add heat to increase plant metabolism.  Finally, the slow currents allow nitrifying bacteria in the substrate to reduce oxygen levels so that the trace elements don't oxidize.  So far, in my experience, the coils have been shown to provide the plants with good conditions for long term growth, but they have NOT been shown to affect the growth rate.  Always the greedy one, I am trying to find a technique to increase the growth rate above the already rapid rate allowed by CO2 injection.  And I may have stumbled on to something.


I have tried to set up the 29 gallon tank in such a way that I can get some fairly controlled results.  I have divided the substrate into two halves (right and left) by glueing a 4" tall piece of acrylic down the middle.  The barrier will divide the substrate into two halves but will allow everything else in the tank to be shared.  I am using two old AquaClear 200s for mechanical filtration and two powerheads centered in each half at the top of the back glass for water movement. Two Tetra CO2 bells are next to each powerhead and fed by a DIY yeast CO2 generator.  A 48" shoplight with a Triton and an Ultra Tri-Lux bulb is centered over the tank, providing light from the top as well as some from the ends.  The substrate is 3" of 2-3mm quartz gravel (Tex-Blast) with Dupla laterite mixed in the bottom third.  With the addition of heating coils, the setup is very close to an "Optimum Aquarium".

I have been following our typical maintenance regimen: 25% water change every two weeks, addition of 1 Duplaplant tablet at water changes, 2 Duplaplant-24 drops every day starting 3 days after a water change, replace evaporation losses with tap water as needed.  The water hardness is maintained at 4.5 dKH and is 3 dGH.  Enough CO2 is being injected to hold the pH at just under 7.0, corresponding to about 15 ppm CO2.

The only significant difference is the way the heating coils are setup in each half.  The right half has 12' of 28 gauge insulated wire, giving about 50 watts of heat with a 12v DC power supply.  The left half is the same, except I have used BARE WIRE instead of insulated wire.

What I am trying to do is this: by creating an electric field in the aquarium, I am trying to force the migration of cations (positively charged ions like NH4+, Fe++, etc) down to the substrate and negatively charged ions like (NO3-) to the top of the tank.  The bare wire has a linear drop from 12v to 0v along its length; it is laid in a paired-serpentine pattern such that the two ends are together giving an average 6v field at that point and the average at all points along the length is 6v.  The DC supply is connected as a -12v supply, so the substrate will have a negative charge with respect to ground.

I was using a "Solution Ground" (titanium probe) at the top of the tank connected to a +6v supply to supply the other half of the field giving a 12v potential from top to bottom.  Since the water potential is only 6v to ground, it should be perfectly safe to work in.  When I was planting plants, I could not detect or feel any electricity at all.

To enhance the effect of the electric field, I am overdosing the tank with a chelated iron compound.  This should greatly increase the conductivity of the water.  I am shooting for an iron level 100x as much as is normal (10 ppm versus 0.1 ppm).

After watching the fish in the tank for awhile, I decided the probe was not the best idea.  The fishes lateral lines are very sensitive to electric fields and they were apparently aligning themselves to the field: they were all leaning toward the probe no matter what their orientation.  A very strange effect, indeed.  To counter this, I ordered some titanium wire from Edmund Scientific and ran a loop around the top of the tank just below the water surface.  This completely cured the fishes tendency to lean.


The tank has been cycled and running for 6 weeks now.  The tank has 6 medium sized M. Bosemani rainbows, 12 otocinclus, 4 corys and 2 small farlowellas.  The fish are fed 1/4 tsp of TetraBits daily.

The two halves of the tank are planted identically and symetrically. Each half has:
  6 stems of Rotala macrandra
 12 stems of R. rotundifolia
  3 stems Bacopa caroliniana
  2 small Anubias barteri
  1 Echinodorus bleheri
  4 E. quadricostatus
  4 Cryptocoryne wenditii
  1 Samolus parviflorus

There were also 10 Malaysian trumpet snails (about 1/2" long) initially. Their population seems to be steadily increasing.


The results so far are nothing short of amazing.

Plant growth is distinctly different on each side of the tank. On the right side (insulated coils or "normal"), the growth is typical of our other CO2 injected tanks: the stems plants need trimming about once per week and the rosette plants put on two to three new leaves per week.

On the bare coil side or "special", the plant growth is more than I hoped for.  It is easily double what the right side has, both in height as well as stem thickness and leaf size and density.  I cannot really justify this growth based on availability of more nutrients; there must be some kind of electro-bio-stimulation going on.  It's as if the voltage potential in the water is supplementing the available light energy to dramatically increase photosynthesis.  There are far more O2 bubbles on the left side plants than the right side.

If this were the only positive result, I would be more than happy. However, as I observe the tank I have been noticing more and more amazing effects.

In a well lit tank, most green plants will have some reddish coloring on the leaves nearest the light.  The plants in the "normal" side exhibit this.  However, the plants in the "special" side have the exact opposite effect: the leaves and stems near the bottom of the plant are reddish and the top leaves are bright green!  About the only reason I can think of for this is the electric field: the Fe++ is being prevented from getting to the top of the plant or perhaps even being repelled by the positive charge at the top.

The Rotala macrandra, normally a plant with a mottled red- orange-green appearance under good light, is exhibiting an even stranger phenomenom.  There are color gradations going from bottom to top: red at the bottom, then orange, a tinge of blue and green at the top. Much like the SDS-PAGE gel procedure, the electrical potential seems to be holding various trace elements at various levels in the plants. An obvious application of this is to grow plants specifically for color coordinated landscape scenes: blue plants for blue gravel, etc.

I have also noted that the Malaysian snails do not seem to live on the special side of the tank.  I have never seen one over there and have not noticed any in the gravel.  I have noted, however, many empty shells just over the acrylic barrier.  It's as if they tried to scale the wall and were zapped when the reached the other side.  An electric fence for snails, as it were.

Fish health has also been affected in a positive way.  When we got the otocinclus, they appeared to infected with ick.  Since they were the only ones around, we decided to buy them anyway.  After being in the tank for a day, we noticed fewer spots on them.  Close observation showed us that the ick was dropping off the fish and was actually being attracted to the positively charged top wire.  Unable to fulfill its normal gravel-living growing phase, the infection was immediately halted.

Water quality was also positively affected.  We monitored the nitrogen cycle from day one and noted that the cycle appeared to complete in 1/3 the normal 5 to 6 weeks and the levels of ammonia and nitrite were very low (< 0.2 ppm each).  We have also not been able to measure ANY nitrate.  We do note a constant low level bubbling at the positive top wire and conjecture that the NO3- is being attracted to it and is being electrolyzed into N2 and O2.  This in itself is a significant advancement in the aquarium State-of-the-Art.

The final noteworthy phenomenom is the affect on algae.  Both sides of the tank have had some minor green beard algae.  The otos have been keeping it under control on the normal side.  The special side seems to have given plants the ability to repel the algae.  If you look closely, you can see small strands of algae growing in the plant leaves, but it is standing straight up.  Under careful observation, you can actually see the algae begin to quiver, detach itself from the plant and head straight for the top wire where it disappears in a little cloud of bubbles!

I hesitate to report the final observation for fear of ridicule, but I feel it is my duty to be as impartial as possible.  I have not yet confirmed the following, but an analysis is in progress.  I will give updates when the final assay is in.

We had some blue-green algae (BGA, cyanobacteria) developing in our discus tank.  With all the positive benefits noted so far, we decided to move the affected plants to the special side of the 29 to see what would happen.  At first, nothing appeared to happen.  We did notice the slime algae beginning to loose it color right before the lights went out and figured it was dying or dissolving.

The next day, it appeared that the BGA had disappeared but on closer examination noted a discoloration of the plant leaves where the algae had been.  They appeared to be a yellowish color.  We removed the plant from the tank and brushed the leaves where they were discolored.  The yellow color came off as a thin film with a metallic sheen.  As silly as this sounds, it appeared to be gold leaf.  We took a few of the samples down to the local assay office and are eagerly awaiting the results.  It looks like this hobby may finally pay off!