Rusty Metal

I've got some very small meccano like shapes plus the relevant nuts and bolts and would like to make a small frame which will be covered in mesh. The frame would hold the mesh about 1/2 - 3/4 " away from the filter inlet which due to the power of the pump (400lt hour) in a 22 litre tank is likely to drag my fishies towards it.  I know this will happen because my grandson has the same tank and it happens in his.

I made a prototype and it's small and neat and due to the shapes I have I can even hang it over the edge to secure it.

I was quite happy with it until my other half pointed out that eventually the metal is likely to rust.

Would this be unsafe for the fish?

I'm not thinking the  fish will got through the filter  (another problem the grandson had) as I have Fluvel sponge behind it, but that doesn't stop the flow.

I've been browsing the web Sue to see what others think and it's very indecisive so on balance I think I'll give it a miss.
Shame, it would have made  neat small frame for mesh and had hanging hooks. We used to have loads of plastic meccano when the kids and grandkids were young but didn't save it.

I've made a box this morning just from plastic gutter mesh which isn't as fine as I would like but by cutting out the corners before I "squared" and secured it I got quite a nice shape.

It seems to be working since the plastic fish are no longer stuck up against the inlet slots.

I also made a spray bar this morning for the pump as the Aquanano 22/30 doesn't have one and I can't find any in stock online.  I was promised a free one from Aquaone but that seems to have gone by the board.

I shall not leave the spray bar in when I finally get fish as I'm not sure it will be good for them BUT, what with that and the mesh cover, the plastic fish are swimming well, albeit in a smaller space.  !!