Got it. Think about this. If you are dissatisfied with the rate of solution when the vial is upright, why not turn it on it's side to some degree so the density difference of the fertilizer solution and aquarium water gives you a gradient to allow the concentrate to flow more readily. That way, you aren't relying just on the water motion to draw the solution out of the vial. You could also use a plastic vial and insert a tube through the bottom and extend it maybe a cm or so. As the concentrate reaches the top of the tube, the density difference allows it to flow down into the tank.
Andrew, MASI Treasurer
This message is always under construction: 75-gallon tank; 2, Eheim 2026 filters - one twice broken; Tek Light with 4, 54W T5s (6000K) ; Sand on top of 4:1 sand:clay mixture; Milwaukee CO2 controller; PlantGuild vortex CO2 reactor; pH = 6.6, kH=70mg/l, GH=120mg/l; EI; Flourish excel on 50% weekly water change: AGA Member.