Everything
@jeffkrol mentioned is good advice. I will add that photography is one of my hobbies. While not every picture I post here is one I spent some amount of time on, there are some that stand out as ones I put a little more effort into.
With the newt tank, most (not all) of the full tank shots were done with my phone (google pixel 4). Most (not al) of the macro shots were done with my real camera (Sony A7III - a 2000 dollar camera, and a 'cheapy' macro lens - 280 dollars).
Additionally some of the pictures (mostly the ones from my real camera) got a little extra TLC in post production with photoshop for things like contrast and to enhance details.
Some macro shots are just done with my phone's 'portrait' mode which uses software to fake bokeh. Meaning the subject is in focus and the background is turned blurry (the bokeh effect). This works really well for images that are viewed on a phone or internet browser but if I were to blow up one of those images to 8x10 size its immediately obvious which is from my real camera vs my phone.
So where does this leave you? Well basically its hard to replicate what I've done with 150 dollar budget if starting from scratch.
The easiest thing to do is to upgrade your phone to one of the multiple camera models (latest pixel, iphone, or galaxy). This might be more justifiable to you since you can use it for more then just photos even though it will blow your budget. (This assumes you don't already have such a phone).
After that I'd counsel waiting and saving more for a camera. Can you buy a camera for 150 dollars? Yes, yes you can. BUT the resulting images from that camera are not going to be a lot better then what a typical phone can take (when viewed on computer screens or phone screens). Ideally you will spend around 500 dollars on a camera. This is enough to get you a mirrorless camera with interchangeable lenses of one system or another (1", 3/4, aps-c, etc). This is one area where buying the latest and greatest tech is definitely beneficial. You can certainly get very very very nice photos using older gear but new compact mirrorless cameras are getting substantially better each year and buying a camera that is 1 generation old is going to produce much better results then one 7 or 8 generations old. That said, I'd only pursue this if you are planning to take pictures of more things then just your fish. If just doing your fish, I'd just use a phone as its hard to justify a fish camera for 500 dollars.
And finally... consider post production as well. Using some software filters you can change a picture that looks 'ok' into one that looks absolutely stunning in just a few minutes. I use the "nik collection" but there are many out there for a variety of software platforms but free and paid.
This is a lot of info.. sorry about that, you touched on one of my other hobbies so I tend to a get a bit verbose.
