Magnetic Platforms for Reef Aquaria

Donya Quick

Introduction

In this guide I will describe how to make “floating platforms” with magnetic algae scrubbers and

rocks or other aquarium-safe materials/ornaments. The interest in pursuing some kind of moveable ledge

for my aquariums came about when I realized just how vertically challenged my aquascaping is. For

various reasons including livestock and tools available, I have never felt confident creating the large piles

of rocks seen in many marine aquaria. As a result, my tanks all have the same pattern: a few large rocks

on the bottom of the tank with bits of rubble here and there around them. This isn’t too noticeable in a 20-

gallon aquarium, but in a 55-gallon tank, the sheer amount of unused vertical space is hard to ignore.

When the tank is stocked full of angry, coral-unfriendly bottom-dwellers but is also begging for corals

with a brand new, 4xT5HO light fixture, the unused space is even harder to ignore.

Figure 1. Cave-loving animals, such as the peppermint shrimp visible only as feelers in this photo, will make use of the ledge aspect of magnetic platforms.

Some people make use of unused vertical of space for home-made frag racks out of egg crate or

the more expensive, clear plastic varieties. These never appealed to me very much, probably because they

are bulky and intended for temporary frag placement. Then, one day, someone mentioned the use of

suction cups to mount individual corals a safe distance away from the bottom, out of reach for angry

crabs. While I don’t trust suction cups for their tendency to fall off at the worst and most unexpected

times, I realized the perfect alternative was right in front of me: magnetic cleaners. And so, I started to

fill my empty vertical space with the types of platforms I present here. The benefits of these platforms

have been three-fold: a place to grow corals in safety, a way to get more light-demanding species closer to

the surface, and a way to provide other animals with ledges to hide under.

This guide is aimed primarily at marine aquarists, although there is no reason that the same type

of platform couldn’t be used in a freshwater or brackish aquarium. In fact, magnetic platforms are

sometimes sold for turtle tanks. However, the constructions I will be discussing are primarily intended for

supporting relatively light loads. Although the idea could be adapted to something like a turtle tank, the

designs I show here would almost certainly require reinforcement to safely support a moderately-sized

turtle.

The photos of actual platforms I present here are also not the most aesthetically pleasing tank

additions possible. As with many things, functionality and appearance tend to be opposites, requiring

some degree of compromise. I tend to favor functionality, so the examples I present here of magnetic

platforms I have made are perhaps not the most beautiful examples of aquascaping to be found, but they

have nonetheless proved to be incredibly useful to me – far more so than my attempts at home-made

plastic frag racks. Also, given slightly more attention to detail, one could improve the appearance of the

platforms shown here with modifications such as extra small bits of rubble carefully placed to hide

exposed magnet corners and/or some sort of complimentary tank background. On a black background, the

magnets might not even need to be hidden much to blend in well.

Part 1: Materials

Magnets

I have often found magnetic cleaners somewhat annoying for the fact that they can be difficult to

move when too strong a magnet is used. For the purposes of constructing a platform with magnets, this

feature is desirable. You want the strongest magnet you can find that meets your design goals. The

stronger the magnet, the less likely the platform is to break free and fall from being bumped. A well-

designed platform should be able to move like an inverted magnetic cleaner (moving it from the in-tank

and the out-of-tank part follows somewhat smoothly) while being non-trivial to rotate downwards or pull

away from the side.

My magnets of choice are the large-size, elongated Marina variety. Individual magnets of this

type have cost me in the range of $7-8 at local aquarium shops. These work well on the glass thickness

present on my 55-gallon tank. Before buying all of your materials, I recommend getting a single magnet

of the type you are considering and doing a “wet test” with it to see how firm the grip is.

When building your platform, it is critical that you KEEP BOTH THE SCRUBBING AND

FELT SURFACES CLEAN. If you allow grit to be ground into either of these surfaces, you will have

just made a lovely glass-scratching device. Make sure you thoroughly inspect and clean all surfaces that

will touch the glass before they actually do. This is particularly important if you are using actual rocks, as

small chips and dust are likely to get on the magnets.

The Platform Itself

When I set about making my first magnetic platform, the first problem I had to overcome was what

material I wanted for the platform part. This is a constraint satisfaction problem. Whatever you use must

have the following properties. It must be:

- Lightweight. The farther out you want it to extend, the lighter it must be!

- Structurally sound. In other words, you don’t want it to be easy to snap in half from light

pressure.

- Appropriately textured, or sufficiently rough. This is important for adhesives.

- Not so long that the leverage from the end substantially weakens the grip of the magnets (what

happens if a large snail wanders to the edge?).

I have tried three objects that met these conditions: resin ornaments, limestone, and rhyolitic tuff (sold as

“tufa”). Each has its advantages and disadvantages.

Resin and other plastic ornaments win in the weight category. They are very light for their size,

unbeatably so as far as rocks are concerned. However, they are problematic in other areas. Even if one

ignores the fact that they tend to look completely unnatural and strange, they are rarely textured in a way

that makes gluing easy. While they may glue nicely to the magnets when dry, gluing things to them while

submerged is problematic and often requires several tries before the object sticks satisfactorily.

Limestone’s main benefit is that it is the same material as regular live rock. Thus, it’s like adding

to your live rock volume once colonized. Dried reef rock has the same advantages. However, aragonite

tends to be rather heavy. Finding a suitably lightweight piece usually means finding a very thin and not

very large piece. While not impossible, it can require digging through rock bins for some time at more

than one store until suitable pieces turn up.

“Tufa”-type rocks have the advantage of being lighter-weight than limestone on average and also

textured in a way that makes gluing very easy. Disadvantages include that these are largely silicate rocks

– so you must take extra care to make sure that dust from them doesn’t remain on the surfaces of the

magnets that will be touching the glass. Additionally, these rocks can be more brittle than limestone due

to their porosity. They do not hold up well to twisting forces. While not a problem for a platform once in

the tank, if you need to move it or remove it from the tank, you will want to avoid just grabbing the rocks

themselves if they are thin.

I recommend using only dry rock and, therefore, avoiding live rock. The reason for this is that

getting a good connection between the rock and magnet requires dry surfaces. This is a problem for live

rock, which must be wet in order to remain live. If nothing else, it makes more monetary sense to buy dry

rock and let it colonize/cure in-tank, since you will probably have to partially kill live rock in order to

make a sturdy platform out of it.

Glue

The main concerns for the glue used is that it must be both strong and aquarium safe. Superglue

(cyanoacrylate) has both of these features and works very well. I have used superglue exclusively on my

platforms. It bonds the plastic on the magnets very effectively and also grips rock well when the surfaces

are clean and dry.

I prefer to use and strongly recommend superglue gel for constructing platforms. The reason for

this is that the gel can be turned into small piles that allow for a larger connection. Gels can also be used

to fill cavities more effectively and maximize the connection surface area that the platform object has

with the magnets. Gels have a longer curing time, but unless you are under some sort of pressing time

constraint to construct the platform, the extended waiting time should not matter.

Figure 2. Motivation for using superglue gel (bottom) over regular superglue (top). The glue, shown in red, will make a better connection with uneven surfaces like rocks when formed into a small mound. While the thin surface of runny-type glue will only catch the tip of the object, the gel will deform around the object and contact a larger area.

Part 3: Planning

Designing a magnetic platform requires some engineering. There are three designs I have tried in

my own tanks: simple, single-magnet platforms; tall, double-magnet platforms; and long, double-magnet

platforms.

Figure 3. Different types of magnetic platforms. From left to right: (a) a simple, single magnet platform; (b) a tall, double-magnet platform; and (c) a long, double-magnet platform shown from the side (c1) and back (c2) respectively, where red indicates glued portions of the magnets.

Simple, single-magnet platforms are the most obvious design to try first and also the cheapest to

construct. However, they are by far the weakest and least stable. This is because there is little to stop the

in-tank magnet from rotating under strain. As a result, the platform must be quite light relative to the

strength of the magnets. If you plan on anchoring anything large/weighty on top of the platform, I

strongly recommend against this design.

The easiest to construct are probably the tall, double-magnet platforms. This is because the shape

and density of the rock are less critical. The use of two magnets also avoids the rotational problem of the

single-magnet design. However, these platforms are also the least useful. They do not offer much of a

ledge or much surface for anchoring frags relative to the size of the rock. They are primarily useful as an

aesthetic feature or for perhaps a single frag.

The third design has both benefits of the other two: it offers substantial space for frag placement

and a ledge for animals to hide under, and the arrangement of the two magnets puts up significant

resistance to any sort of rotation from pressure on the end of the platform.

Of course, this is not the end of possible designs. Any number of magnet and platform

configurations could be used, each with their own advantages and disadvantages. Regardless of the design

used, the important things are to ensure that the platform is stable under whatever strain it is expected to

experience.

Figure 4. A magnetic platform made from a resin ornament and encrusted with Zoanthids (left) and a platform keeping a coral frag safely away from a large hermit crab (right).

Part 4: Picture Walkthrough

Step 1: Planning.

It is always a good idea to start with a plan, as it will affect what types of materials you gather

(shapes of the rocks, etc.). The following MS Paint doodle was my original plan for this platform.

Magnets are shown in gray, rocks in orangey-brown, and glued areas as black blobs.

Step 2: Materials.

I chose to use two large, long Marina magnets and acquired three pieces of tuff/tufa. I ultimately

only used two of these rocks, but purchased all three because dry rock is cheap and I couldn’t be sure at

the store which two pieces would be the best fit.

Step 3: Gluing the Magnets

Take the in-tank portion of the magnets and glue them in the orientation you want.

Keep them away from the out-of-tank halves at this time. Once the glue is cured, turn the glued

halves over (scrubbing side up) and place a Ziploc-type sandwich bag over them. Place the out-of-tank

halves onto the in-tank halves to line them up, keeping the bag between them and ensuring that the bag

doesn’t wrinkle between the out-of-tank halves. The presence of the bag is important as it ensures that

glue dribbles or uncured sticky bits from the previous gluing won’t lock everything together by mistake.

In a worst case, the bag would need to be cut to separate the in-tank and out-of-tank portions (the reason

why you actually want two layers of plastic, not one).

The important thing at this step is to MAKE SURE YOU GLUE BOTH THE IN-TANK AND

OUT-OF-TANK PARTS THE SAME WAY. Using the method described above will facilitate this,

since you can line the out-of-tank side up using the other side as a template. The last thing you want to do

is wait for the glue to cure and find out that the magnetic halves don’t line up properly.

When the glue has cured, remove the out-of-tank portion.

Step 4: Gluing the Rocks

Turn the in-tank portion of the magnets scrubbing side down. Arrange you rocks as you want

them and make sure the configuration has several points where the rocks touch the magnets and each

other. Ideally you want to be able to balance the rocks in their final configuration. This is what I have

done in the photo below.

If you can’t balance your rocks, you will need to clamp them in some way during gluing. When

you are certain you have a good arrangement, remove the rocks, place large mounds of glue at contact

points on the magnets, and then place the rocks one at a time. Look at the construction from the side to

see if there are any areas that could be filled with superglue gel to give a firmer grip between the rock and

magnets. Use the tip of the glue applicator to spread glue and force it into small spaces. Be sure to place

glue anywhere the rocks touch each other for added support.

Wait several hours for curing before testing the stability of what you have built, otherwise the

rocks will probably pull free and leave a gooey, stringy mess of uncured glue.

Part 5: Dry Test.

Once the glue has cured, you can do a dry test by connecting the in-tank and out-of-tank magnet

halves. YOU MUST DO THIS CAREFULLY!!! The magnets will exert a lot more force when in direct

contact than with a pane of glass separating them. Particularly with the type of rock I have used here, the

force from the magnets can be enough to damage the rock if the magnets shift suddenly in one hand while

the rock is held firmly in the other.

Hold the out-of-tank portion only and observe that the platform is steady. Push on the platform

with your other hand to test its stability. If you encounter any problems at this stage, you need to resolve

them before moving onto a wet test.

Part 6: Wet Test

Now that your platform has passed a dry test you can move onto a wet test. Carefully separate the

out-of-tank halves of the magnets and MAKE SURE THAT THE FELT AND SCRUBBING SIDES

ARE FREE OF DEBRIS. Place the platform in the tank in an easily-accessible location where a fall

would not damage anything and line up the out-of-tank halves on the other side of the glass. Once lined

up, reach into the tank again and push on the edge of the platform.

On a platform such as the one that has been shown here, you should encounter significant

resistance and not be able to make the platform rotate even with moderate pressure. If a light bump causes

your platform to rotate visibly, you have probably put too much weight on the magnets or the magnets are

not powerful enough for your glass thickness.

If your platform passes these tests, it should be ready for regular use. Good luck and happy

reefing!