What glue is safe to use?

I have a Fluval Evo 52 l aquarium which I use for freshwater. The flow over the media is poor and there are a couple of vents which I need to close somehow to improve this. I’ve tried a temporary solution and it works so I’d like to make it a permanent fix.

I’m thinking of using small oblong pieces of plastic, 15x100mm glued in place to block the vents. But before I break out the Superglue, I thought it best to ask advice on a safe and perhaps more appropriate glue. This will be a plastic-to-plastic contact — not on the glass.

JEREMY REPLIES: I don't usually hear of poor circulation in the filter section of Evo tanks. You could use aquarium silicone, or Superglue gel but I'd be careful what you're sealing up — they may be there to prevent the filter chambers from overflowing. If nothing is cracked or has come away from the tank glass, I would be inclined to leave the design of the filter box as it is and just place a more powerful pump in there instead. Sicce produces lots of tiny pumps that should suit an Evo perfectly. Experiment with removing mechanical filter media like sponges too, as that may be impeding the flow the filter. Replace with ceramic rings, for biological filtration.