When I wrote my page on replacement parts for Fluval Spec aquariums, I had pretty good success finding sources for most parts. The one mystery was where to get replacement hose for the flow tube. Some people who were interested in the flow tube modification were concerned that if they botched the job a replacement would be in order. It is not a hard mod, but I wanted to put people at ease and I set out to find a good source for replacement. However, this has turned out to be a bit harder than expected.
To back up one step, the part in question is a little rubbery tube connects the pump outlet to the elbow at the flow nozzle.
I will cut to the chase and give you the only source I know of for an exact replacement. A very kind reader reported that if you order the output nozzle from Hagen’s website, they include a replacement flow tube. This isn’t clear from the product description, and I haven’t confirmed this myself, but that is what the good readers report. This is great news. It is not that expensive (shipping cost much more than the part) and it is a direct and exact replacement in size and material.
The real fun is in finding a source for hose on your own.
Replacement Flow Tube Hose – What to Look For:
The basics is that you are looking for Food Grade Silicone Tubing. This is the material used for the part. Food grade implying that it is safe for use with your fish.
The real fun comes in finding what size Fluval uses with their aquariums. Hose is sold in various sizes. The size is indicated with two numbers. The first number is generally the inside diameter. The second number is the outside diameter. The food grade silicone tubing is here is a rundown of what I have tried and how it fared. (click on image below to enlarge)
- 9mm ID x 13mm OD: A reader suggested this and seemed to think it fit. I don’t know how he or she got it to fit. The inside diameter seems entirely too small to fit over the fittings at the pump / elbow. Next!
- 1/2″ ID x 5/8″ OD: I did some conversions from metric to english and it seemed a 1/2″ ID hose would work. Technically, it does work. The wall thickness seems to match; however, the ID is a bit larger than the stock hose. Bottom line is that it works – it’s just not exact. I would be a bit worried long term that it will loosen and not hold tight over time.
At this point, I decided to contact Fluval and ask them about the hose. Here is their response:
Dear (Spec-Tanks owner guy),
We thank you for taking the time to contact us.
It is 7 3/8″ long the ID 3/8″ OD 9/16″.
Customer Service Dept.
Rolf C. Hagen (USA) Corp.
So here we go – getting somewhere! Off to get the size they describe.
- 3/8″ ID x 9/16″ OD: Still doesn’t match! Wall thickness is thicker than the stock and the inside diameter is slightly smaller than stock. It does work but is a little bit tighter to fit over the fittings.
So where does that leave us? For metric, I’d guess the correct size is something like 11mm ID x 14 mm OD. For english, a best guess would be 7/16″ ID x 9/16″ OD. I’m done hunting down hose for the moment. If you don’t want to get the Hagen flow nozzle part that comes with the hose, I would suggest sourcing 3/8″ ID x 9/16 OD as it is the best function and fit of those that I have tried.