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I am building things to go in saltwater aquariums, so they need to sink, to be more dense than 34ppt seawater (roughly the same as the sea). PLA is no good as it will degrade due to bacterial action, ABS floats, I don’t want to trial and error every type until I find one that sinks!

I am using the ord solutions RoVa3d printer.

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Hey Tony,

how about metal filled filaments like the brass/bronze/copper from Colorfabb or Protopasta’s stainless steel? They all have densities above 3.5g/cm^3.

Sincerely,

Jonas

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Thank you for your suggestion - unfortunately marine life is very sensitive to metals, particularly copper. I’ll have a look at the steel one, though would even stainless steel not corrode if constantly exposed to seawater?

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Why not leave room in the model to mount a rock? Or print in a metal filled filament and then coat it in something like alumilite clear cast.

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That will be my fall back, I tend to use glass marbles if I need to weight things down, but it would be more elegant if I could just print in a denser plastic, if one exists.

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In theory (actually according to phisycs) assuming I’m not pulling a NASA and screwing up units or conversions. Water is 1g/cm3 Salt water is 1.025-1.05 ABS is 1.04 PLA is 1.25 PETG is 1.38 So PETG should sink and survive in saltwater. Your model would have to be solid plastic or specifically sliced to allow water to fill in all the air pockets. You could stick the part and some saltwater into a vaccum chamber at 10/20 to pull all of the air out and replace it with water.

1 Like
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Smashing, thank you. I shall try some PETG.

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I would suggest PET also

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I agree with Jonah, print at close to 100% infill or allow for water to fill your models should sort out the floating issue

I have PLA in my tropical tank for years and haven’t noticed any issues, have you tried PLA in your salt water before? (if i recall correctly PLA needs around high 60s centigrade to start degrading)

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this might be interesting to you

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Interesting - I’ve not had pla long term in a salt water tank, it was Internet research has suggested degradation would occur. But it makes sense, there are bacteria that need a carbon source and pla looks like just the right sort of compound to provide it for them (similar to vodka dosing or ‘bio pellets’ where this phenomenon is deliberately used to remove nitrates). But ive not demonstrated the problem.

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WHY NOT FILL THE INSIDE WITH GRAVEL HALFWAY THROUGH PRINT AND USE NO OR LITTLE INFILL

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I WOULD ONLY TRY STAINLESS STEEL AS THE OTHERS WOULD POISON THE AQUARIUM

http://www.mes3dfilaments.co.uk/product/proto-pasta-stainless-steel-pla