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conor puckly

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Dec 3, 2018
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I have two Oscar's and two bristlnose plecos and was wondering what would be the best choice of large aquarium rocks the put in my tank.

I have a 75 gallon tank wide
I'm also going to put a diy bubble bar in the back of the tank

Is it possible that I can put a natural obsidian rock structure or no
Here's what the tank looks like


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I think that would fit. You could also use dragon stone if you don't mind the cost; some driftwood and hard-leaved live plants would look nice in there too.
Do you think the obsidian rock will ruin water ph or hurt my oscar fish because sometimes I feed them feeder fish that I breed in a seperate tank
Would highly recommend at least 75 gallons for each of your Oscars long term, with a 5 or better yet a 6 foot tank for each.
Even in an 8 foot tank, there are some adult oscar that do not tolerate any tank mates at all.

Even if there are no conflicts now, Oscar aggression goes up significantly when they reach adulthood.

As to the decor, obsidian is natural glass, and was often used for knife and spear blades before the discovery of metalworking, so check very carefully for sharp edges before using it.
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Assuming "obsidian" refers to the volcanic glass-;like rock, it should be inert and not affect parameters so safe from that aspect. Make sure there are no rough edges, something that may be next to impossible to achieve. Given the fish, Oscars, why not consider an authentic habitat aquascape? Lots of chunks of wood and branches. Floating plants would help, even if they get somewhat eaten, they usually reproduce fairly rapidly.

Oscars like to rearrange their environment, so they will dig into the substrate wherever they fell like it, and any rock structures should therefore be placed on the bottom glass with the sand built up, and not on sand that could be undermined causing the rocks, if stacked, to fall, cracking or breaking the glass. Wood would not cause the same danger.
Agree with Byron on being careful with anything hard added to the tank, Adult oscars are surprisingly strong, even considering thier large size.
Large adults have been known to frequently break glass heaters.

If you get a new tank in the future, it might be a good idea to use aquarium safe silicone to attach any rocks firmly to the glass, and give it 2 or three days to cure before adding water
I had a 12 inch Oscar in a 125 gal tank he would rearrange the tank daily I had slate rock and finally had to silicone them together to get him to stop moving them and they were not small roughly 12 inches each he did not tolerate any tank mates except a pleco which grew to over 12 inches also

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The above comments are all good recommendations. I too would recommend a 75g for only one oscar. These are big and messy fish that produce a ton of waste. Based on my experience with oscars, I'd be most concerned with the insane bio load that they produce (and 2x plecos are poop machines to top that off and also heavily contribute to bio load) They are looking good and healthy right now. I see some nice growth on the fins.....but they still have lots of growing to do!

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