Substrate And Rocks

Bought a used 36 G bow front aquarium. It came with substrate and rocks. Can anyone tell me what type of substrate and rock these are? I am planning to build a community tank with angelfish, tetras, cory catfish, red tail shark. The substrate doesn’t look like gravel nor sand. It seems to have grind crystal and lots of shells. Don’t know if it is safe for bottom feeders. Also Wonder if I can reuse those rocks. They seem to have very rough edges. I am worried about damage angelfishes fins and tails. Almost seem like a saltwater setup but the seller told me he used to keep cichlids. Any idea?

 

Substrate looks like mixture of gravel + crushed coral. Definitely not good for cories.

Edit:
Is that lava rock?

 

Substrate looks like mixture of gravel + crushed coral. Definitely not good for cories.

Edit:
Is that lava rock?

Thx. crush coral makes sense. need to throw those away and go with eco-complete base layer and sand top lever. have no idea what type of rock that is. Probably going to replace those with driftwood too

 

They all look like pieces of coral. If that's the case then it makes sense if it was for a cichlid setup, an African cichlid setup, as coral is known to buffer alkalinity and hardness. Which is the opposite of what you want for south American species, much of which your stock plan are save for the shark.

Speaking of which... I do apologize for speaking off topic, but I don't recommend a rainbow or red tail shark in a tank any less than 48" in length. Both species get 5-6" long and become highly territorial of the bottom surface area once they reach about 3". In your tank size, I can tell you that a shark will do excessive chasing in no time at all and cause its tank mates a great deal of stress.

Best of luck.

 

They look like Texas holey rock to me. There are some good s of it on ebay, where I bought mine. Can't remember which vendor. I have it in a tank with a betta and african dwarf frogs. No problems with fins or frog's skin and the nerites are cleaning the brown algae off of it!

 

Q: What happens when someone throws a rock at you?

A)You hit rock bottom.

File the rocks.

 

They look like Texas holey rock to me. There are some good s of it on ebay, where I bought mine. Can't remember which vendor. I have it in a tank with a betta and african dwarf frogs. No problems with fins or frog's skin and the nerites are cleaning the brown algae off of it!

Did more research online...it doesn’t look as smooth as Texas Holey rocks. I think they are coral based rocks

 

Did more research online...it doesn’t look as smooth as Texas Holey rocks. I think they are coral based rocks

I just saw them on Pinterest described as "coral based limestone"! Didn't know there was such a thing. Anything else you uncover would be useful!

 

Update: decided to use existing substrate and rocks. and going to stock with African Cichlids




Rocks in