I use the controllers I buy from the auction site but any controller will need some form of probe in the water to sense the temp. One way to hide it is to place it in something like a wooden item, another is to place it in something like a soda straw which can be the best color to hide and it also makes it easy to silicone or super glue flat to a place like a corner or near the bottom where it is hidden behind things like plants. One advantage to the soda straw is the ease of sealing it from the water. Technically they are water resistant, often mislabeled as water PROOF, but there is a difference! I find they last longer when placed in a straw and the end sealed. Easy to set the straw on fire and then clamp it out which leaves the plastic mashed/sealed.
If the wire over the edge is a problem adding a bit of plastic fitting in the tubing and sealing the probe in that will let it sense and not show.
Inkbirds are great but the cheapo hit the wallet much more gently. The difference is in how you feel about the DIY portion.