Got two Chinese Algae eater and two Black Mollies to finish the algae.
Plants are pearling.
Transferred the Guppies back to my original guppy tank after 4 days.
Now my tank 350 .0 L (approx 93.0 gallon) has
1. 5 Harlequin Rasbora
2. 4 Serpae Tetras
3. 2 Siamese Algae Eater
4. 3 Black Mollies
5. 6 Penguin Tetras
Will wait for at least 5 days to get new fish.
Next will be
How many more fish can I add?
How many fish you can add is a tricky question to answer. It's not just about numbers, but also how big they get, how they behave and interact, where they hang out, what parameters they prefer and so on.
As it is, you've already added small groups of schooling species (the rasbora and tetras) that are both happier and way more fun to look at in much bigger groups. In a tank as big as that, you could easily keep a huge school of small fish - but that means you have to restrict the number of species you keep, because you can't keep three huge schools!
The siamese algae eaters get BIG - 15 cm - so that's something you need to take into account for the future.
Finally, you haven't said what kind of rainbow you were planning on adding, and I'm by no means an expert on rainbows, but if I recall correctly rainbows tend to want hard, alkaline waters, whereas the tetras and rasbora all want soft, acidic water.
If I were you, I'd slow down on adding more species and think carefully about the composition of your tank. Ideally, you want fish that occupy different levels of your tank - some that hang out at the bottom, some mid column, some at the top. You also want to try to keep fish that like similar parameters, so you don't end up with some of the thriving and some of them just barely hanging on.
Try plugging your ideas into AqAdvisor - Intelligent Freshwater Tropical Fish Aquarium Stocking Calculator and Aquarium Tank/Filter Advisor
and see what it says. There are no perfect calculators but aqadvisor has most of the common tropical fish species represented and will give you some idea of whether you're on the right track.