I would omit the Siamese Algae Eater. This is most likely the species Crossocheilus langei, which is a shoaling fish by nature, and it does best in a group of 6 or more and a distinct hierarchy will be formed within the group. As it attains six inches, this has consequences.
This fish occurs in flowing waters and is intolerant of high nitrates and any build-up of organic waste, requiring clean, well-oxygenated water; it is an active swimmer and thus needs space. It will therefore be best in a river or stream aquascape having a reasonable current from the filter along with a substrate of gravel, sand and pebbles, with larger rocks simulating boulders and some bogwood added. As noted above, it should be kept in a group of 6 or more so that the natural interaction between fish can be enjoyed.
However, your other fish (hatchetfish especially) are not going to fare at all well with strong currents that the SAE must have. Nor will they appreciate its active behaviours (the rainbows may find this annoying too). Another two reasons to omit this species.
For those who like taxonomy...Crossocheilus langei is the species most often encountered in the hobby as the "Siamese Algae Eater" [SAE] and is the best at eating black brush [aka red beard] algae. The "true" SAE is actually Crossocheilus siamensis, a species initially described by H.M. Smith in 1931 as Epalzeorhynchus siamensis and moved by Banarescu into the genus Crossocheilus in 1986, and which has probably never been seen by hobbyists since the holotype [the specimen collected and used for the description] is the only one known. To further confuse, the fish described as C. siamensis by Smith was subsequently determined to be conspecific with a prior described species, Crossocheilus oblongus, so in fact there never was a C. siamensis as a distinct species, and the name now is a synonym for C. oblongus.
