One modification that some people are interested in for the Fluval Spec aquariums is to add a cover over the overflow slots that lead into the filtration systems. This can be useful for those wishing to breed shrimp or fish and want to keep those critters out of the filtration system. It may also be beneficial for owners of betta fish who’s long fins can get caught and torn in the return slots.
I had thought that the best way to obscure the openings would be to affix some sponge blocks over the edge to cover the slot. I never have gotten around to try this; I think the resulting piece would be difficult to keep in place and wouldn’t look good. I found an alternative in a Spec Mods forum to use stainless steel mesh as a cover over the return slots. This seemed like a good solution and one I wanted to try out.
The good thing about this mod is you can make it yourself. The slightly tough part is finding the stainless steel mesh material, but I will discuss that more below. Another plus is that a stainless steel cover will be reusable; it is durable and rust resistant so you don’t have to worry about it wearing out like a foam piece would.
Materials – Where to Source Stainless Steel Mesh:
Stainless steel mesh is available in differing opening sizes. This is designated as the mesh size, which is the number of openings per inch. 10 mesh has 10 openings per inch; 50 mesh as 50 openings per inch. For our application, we want a balance between a very fine mesh (small openings) that will be soft on fish fins and keep out the smallest of critters and a more coarse mesh, that will be stiffer (easier to work with – more durable) but would let in very small criters.
The tipping point seems to be around a 20 mesh, which is what I bought and will recommend. Look for a stainless steel type of either 304 or 316; either will resist rust and corrosion, but the 316 is slightly better in this regard.
There are many sources for stainless steel mesh online. I got mine from Amazon: Stainless Steel 20 Mesh, 15 cm x 15 cm.
Here is what you will need to make your own return slot cover:
- (1) piece of stainless steel 20 mesh, at least 10cm x 10 cm
- A pair of scissors
- A Ruler (I prefer metric for the scale of this work)
- A straight edged object with a thickness of around 2mm (such as the back of a large kitchen knife)
- Optional: bench vise
How to Form the Stainless Steel Overflow Cover:
The concept is simple – you just need a flat piece of the stainless steel mesh cut to size to cover the slot openings in the overflow. The design is to cover one side of the slots and have a small piece overhang the top and the other side to hold it in place. (never mind the shrimp inside the filter section in the photos – they snuck in before I got the screen in place!)
The good news is the stainless mesh is easy to work with. It stays fairly ridged as you bend it, but it still holds its shape. You can cut it with scissors. The mesh forms a very nice grid that is easy to follow along for a straight cut.
Step one is to cut to size to cover your slots and allow for a bit to go over the top. I cut mine (for a Spec V aquarium) to 95mm wide and 55mm tall.
Once it is cut, you need to find a way to put the bend at the end to hook over the top of the return slot baffle. You could just bend it right over the aquarium baffle to form it, but the forces might cause you to damage your aquarium. Better is to bend it around another object of about the same thickness as the plastic of your aquarium filter baffle.
I measure the overflow baffle at around 2mm thick, so any straight object of around 2-3mm thick will do. I found a good kitchen knife with a flat back edge that did the trick.
Since I have available a bench vice, I used that to put the final squeeze on it to form it around the template.
See the photos below (click to enlarge) for dimensions of where the bend is located:
The dimensions shown are for a Spec V. I have also confirmed that these dimensions will also work with the Spec III. It is not an exact science as I just designed it to overlap the slots by 5-10 mm.
Installation and use:
It’s very easy to install; just hang it over the edge. You can have it either with the main cover inside the display tank or inside the filter section.
Water still flows freely through the mesh and doesn’t affect filtration negatively at all.
If you bend it correctly, it stays flat to the baffle and doesn’t allow critters up into the edges.
The photo above shows the overhang in the display section and the stainless cover inside the filter section. I found it a bit difficult to get the mesh inserted down next to the sponge filter and I think I prefer the opposing mount with the mesh inside the display tank. However, the tight fit against the sponge might ensure that nothing can get in; there is sometimes a gap between mesh and filter wall with the mesh installed in the display tank.
While the mesh is a metal, it is fine enough to be soft and will not cause trouble to fish fins if they brush against it. I have only had it in place for a short time, but I have not noticed any corrosion, which would be unusual to see from 304 stainless steel.
This is a Spec mod that does involve a bit of handiwork to fabricate, but I think many people would be able to do this themselves. My use of a bench vise helped greatly to get the bend nice and crisp and I think this really helped the cover stay flat and clean.
For those that absolutely want to keep fish fins, shrimp or fish fry, adult shrimp, or snails out of the filter section, this is a great mod. I went through this process to try and help those out with this need. However, I don’t expect the cover to be a permanent install in our tank. I don’t have a fish species that is bothered by the overflow slots. I also don’t care about shrimp getting into the filter section. It doesn’t ever seem to do them harm, even baby shrimp. They seem to always make their way out and are safe.
However, if you are one that has need for an overflow cover, I hope this helps you out in your planning and execution. You may even use this to come up with a better solution – let me know!
Edit: Since I first wrote this, I have found another very useful reason to keep this filter cover on our tank. When I trim our plants, especially the very small leaves on the HC Cuba, the tank can get flooded with plant bits. Having this in place helps prevent many of those bits from getting into the filter section. For the days following my trim, I daily turn off the pump, remove and wash this screen (to dislodge the plants that are built up on it), then replace. In a few days and a few cycles of cleaning, the plant bits are removed from the tank and the filter section stays clear.