Review: Dennerle Dosator


Editor's Picks

Nathan Hill checks out this new nutrient dosing device for aquarium plants.

Oh, this is clever. A slow release dosing mechanism for nutrients that doesn’t rely on a cumbersome peristaltic pump. 

How does it work? Science! There’s a semi-permeable membrane at the bottom of the device, through which water slowly seeps, pushing the water/nutrient mix up and out into the tank via a tiny spout. There are no moving parts as such, but you do have a syringe action on the dosing part of the device. 

Using it is simple. Add liquid — either Dennerle S7 VitaMix or V30 Complete (in accordance with the instructions) and away you go. 

Well, I lie. First of all you need to prepare the membranes according to dosage and ingredient.

You have a selection of options from 50-250 l for both liquids, and you need to get this part right — mess it up and you’ve ruined your membrane. It is as nerve wracking as defusing a nuclear bomb in a building full of newborns. 

Then with the right membrane in place, you add your liquid, push the plunger/nozzle in so that there’s no air and the liquid is partway up the spout, and then place the unit in the tank, about 1cm above the water level. After 12 hours your solution should be (incredibly) slowly dripping in to the tank. 

On the one hand, I’m thinking this is the product that nobody really asked for, which seems a tad more awkward than just making up an EI mix and belting it in daily. On the other hand, it’s early days, and it may turn out that a steady, slow dose of nutrients might be better than fluctuations and help to reduce algae even further. We shall see, I suppose. 

Does it have a market? Yeah, why not? For those who prefer a softly-softly approach to the gung-ho bucket science of EI this will be a great relief. I’ll be especially keen to see how the product develops for other chemical uses too. I imagine that if it behaves the same with glutaraldehyde, acid and base solutions or fish medications then it’ll really end up going places. 



Early signs are promising but I’ve not had one running long enough to be conclusive. Could be great, could be a donkey. Tough to say at this stage. It is fiddly for what it is, I must confess, and I imagine the novelty of frequent refills will soon wear off. 

Ease of use:




Value for money:


Overall score:



RRP £9.85.

Why not take out a subscription to Practical Fishkeeping magazine? See 

our latest subscription offer.

Don't forget PFK is also available in digital format. 

Click here

for more information on the iPad or iPhone version.


click here

 for details of the Android version.