would this be safe to use inside the aquarium as a tunnel

[SALTWATER FISH HIPPIE]

https://www.zoro.com/zoro-select-wye-4-in-hub-1whv8/i/G1530006/?utm_source=google&utm_medium=surfaces&utm_campaign=shopping%20feed&utm_content=free%20google%20shopping%20clicks&campaignid=21447546414&productid=G1530006&v=&gad_source=4&gclid=Cj0KCQjw0Oq2BhCCARIsAA5hubWhQIFSplr-qqVOiPnTTqvnnNxUS1dO9mJHY7IaabWdQ5HxExZFYn4aApCuEALw_wcB&gclsrc=aw.ds

 

[FUNGI]

yes

 

[IceNein]

Also yes. These are what people recommend to put in quarantine tanks because you don't want rocks. Do you plan on covering it with rock work and just using that as the structure for the tunnel?

 

[Schulks]

Any PVC fitting would work and would be a lot cheaper. You can find an assortment of fittings at home supply stores for 2-4 bucks.

That one is made of ABS which also works.

Edit: I was not paying attention to the size. nevermind