can i put anything from my backyard and put into my fish tank?

The wood is not not advisable, as the tiny little decomposers within the wood, (even if its dried) can pollute the water, carry algae, and make the conditions dangerous for your fish. The wood may also contain mites or insects that may carry disease. Wood isn't meant to be in water, as it will decompose. The wood you see on the beach is saturated with salt and hardened with sunlight and so it hasn't decomposed because it has been preserved, but they are a no go also, as I'm guessing your fish are freshwater fish.

by "rocks", if you meant sandstone, limestone or anything grainy or relatively "soft" (easily broken), don't put it in as it too can contain impurities or minerals that can kill your fish if they spread. But, if you have smooth pebbles or other hard, smooth rocks that don't crumble and look fairly pure (one substance, not a mixture of rocks), as you said, run them under boiling water, and test them in a bit of your tank water before you add them to your fish forest.

Take care, and use your own observations, dont put anything in if it looks unclean, impure or organic (was once or is alive).

I hope all goes well.

Hint- take a look at your local pet shop's gear that they put in their fishtanks, see if theres anything they have that you could easily get from your backyard, and, if youre up to it, ask the pet shop assistants, they are usually in the shops because they love animals, would probably be happy to give you some tips, if not answer any questions about your own backyard subanstances' suitability for fish.

You have slipped a few decimal points on you calcs. 154 litres is more like it. Still a useful tank of course, but no exactly HUGE. You just need a heater and filter suited to that size tank, maybe 150w heater and a suitable filter. Question is what fish do YOU like? A couple of medium size fish (gourami or cichlids maybe) A whole heap of smaller community fish? Just remember the tank is really only "medium" sized. Lots of common fish will actually outgrow it. So no Oscars, Bala sharks etc. Ian

Kind of: but you don't want to put any seashells in a fresh water tank. Also I wouldn't recommend placing wood in your fish tank, too much debris and could clog your filtration system. Rocks are fine! Rinse well!

I wouldn't as fish can die really easily even from the littlest bit of poison in their water. You can buy things for their tanks from pet shops so that they can hide and play in them. It's better to be safe than sorry and buy them!

No , you need plants that are grown for water immersion in fish tanks...

There might be parasites on the ones from the yard, chemicals, pesticides.....

Please do not put them in......

Generally it is recommended that you boil it before you put it in your tank.

I have used rocks and wood that I found - so far so good :-)

im wouldnt fish can die really easily with diseases

there are million of different types

personnaly, i wouldnt

Yes but you should actually boil it first to kill everything that is on it.

Yes, you can but i would advise against it.

i think they will like the lawn chair