Ultrapure water filter with colour indicator.

The Aqua Medic Top End Filter  is an ultrapure water filter designed to be placed downstream of a reverse osmosis (RO) system. Its primary goal is to remove trace silicic acid or silicates (residual silica), plus other very small ions that RO units may not fully eliminate. It’s particularly useful in marine aquariums, where even low levels of silicates can lead to issues like diatom blooms.

High levels of silica (silicates) in tap water are often a problem in the aquarium hobby despite the use of the most modern reverse osmosis systems. Even with retention rates of up to 99%, a residual silica concentration often remains in the pure water that can lead to problems with diatoms especially in saltwater aquaria.

The Top End Filter is placed directly behind the reverse osmosis unit so that any remaining silica is removed from the ultrapure water. The filter includes a colour-indicator ion-exchange resin so you can visually see when the resin is becoming exhausted and it's time to replace or recharge the media. The binding capacity is exhausted with approx. 1,800 l water flow (depending on the water quality).

• Silicate removal: Targets residual silicates that RO membranes often leave behind (even with up to ~99% retention).

• Colour indicator: Resin shows visually when its binding capacity is nearing its limit.

• Ready to install: Comes filled, mounted in its housing, with everything needed for installation behind the RO unit.

What’s Included

The product comes with:

• The filter housing already filled with ion exchange resin (with colour indicator).

• Wall bracket for mounting.

• Bracket to attach to an existing reverse osmosis filter, e.g. Aqua Medic’s Easy Line.

• High-quality 6 mm connection fittings.

• Grid plate with microfilter.

• Microfilter sponge.

• 50 cm hose.

Technical Specifications

• Diameter: approximately 71 mm.

• Height: approximately 330 mm.

• Filling capacity (resin volume): approx. 500 ml.

• Binding / working capacity: the resin holds up until ~ 1,800 litres of water have passed through (this depends heavily on your water’s quality, how many silicates, etc.).

How It Works 

• After water has been purified by RO, it's passed through this “top-end” resin filter to polish out remaining silicates or trace ions. This helps avoid microalgae/diatom growth and helps maintain ultra-clean freshwater or saltwater for sensitive organisms.

• The ion-exchange resin uses different functional groups (OH-form and H-form) to exchange ions in the water, trapping unwanted silicates, etc.

• The colour indicator gives a visual cue when the resin is spent (i.e. when it’s time for replacement).

Pros:

• Great for achieving very low silicate levels, which is especially relevant in marine aquariums.

• Colour indicator is very useful—it prevents surprises.

• Compact enough to add onto many RO setups; all necessary fittings included.

Things to Watch:

• The 1,800-litre capacity depends heavily on your input water quality; if your tap water has high silicates or many interfering ions, the resin will exhaust faster.

• It’s an extra cost/maintenance item: you’ll need to replace resin when spent.

• The connections are relatively small (6 mm hose), so ensure they're compatible or you might need adaptors.

Ingredients:
-    Styrene-divinylbenzene copolymer with trialkylammonium groups in OH form
-    Styrene-divinylbenzene copolymer with sulfonic acid groups in H-form

Safety instructions:
P280 Wear protective gloves/clothing and eye/face protection.  
P305 + P351 + P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove any existing contact lenses if possible. Continue rinsing.

Safety & Handling

• The resin materials include styrene-divinylbenzene copolymers with different ionic functional groups (trialkylammonium in OH-form, and sulfonic acid in H-form).

• Hazard warnings: H318 (causes serious eye damage) among them.

• Safety instructions include wearing protective gloves, eye protection, and if resin comes in contact with eyes, to rinse carefully, etc.