One tip that I offer on my page on keeping Betta fish in a Spec Aquarium is to put filter foam over the return nozzle to help reduce the fast currents in the Spec aquarium. There are probably several situations where the fish/inverts might benefit from reducing the very fast velocity of water that comes from the stock Fluval Spec Nozzle.
For those that don’t want to make something from scratch, I had suggested you use a Fluval Edge Pre-Filter Sponge on the nozzle. I decided that I should try this mod out to see how it works.
Fluval Edge Pre-Filter Description:
The part is very simple. I’m not sure what exactly it does on the Fluval Edge aquarium, but it is a simple cylinder shaped piece of coarse, black foam. It has another cylindrical cut-out in the center, but not all the way through.
It is a bit larger than expected. I measure my sample as:
- Diameter: 40mm (1.57″)
- Length: 70mm (2.76″)
- Hole Diameter: 15mm (0.59″)
How to Install:
Gosh, the simplest mod yet. You just put the hole in the sponge over the end of the nozzle. Done.
Just like that, flow goes from fast and harsh to slow and gentle. The only real trick is that it tends to float a bit when it is dry. First dunk it in the aquarium and give it a squeeze under water to get the air out. Then it will be less buoyant and will rest in a neutral position.
Performance – How Well Does it Work:
As a simple modification to make your flow hospitable to a betta or other sensitive fish, it works great. The flow velocity is greatly reduced. The picture below shows the stock nozzle. You can see the ripples in the water that hint at the flow speed from the nozzle.
The picture below is with the pre-filter sponge over the nozzle outlet. No more ripples.
Even better is this video. It shows several angles of the tank with and without the foam diffuser:
The velocity is absolutely tamed with the piece of foam installed. I questioned if the flow rate (actual quantity of water) was reduced, but I don’t think it is; possibly just a tiny bit. It is really just a change in quality of water flow, not quantity. The stock nozzle is like holding your thumb over then end of a garden hose. With a sponge over it, it’s like a slow spray wand attachment on a hose. Same flow, just diffused in all directions instead of blasting in one focused jet.
For those that want a more gentle water pattern in their Spec for little effort, this is a good option. The only negative is that the Fluval Edge Pre-Filter is actually quite big for the scale of this tank. Ascetically, a smaller sponge would be better, but it is still not all that bad.