I apologize but I haven't read the entire post. I am answering your question based on your initial post so I hope I don't turn over stones that have already been worked through. In a tank your size the main aspect of keeping a mandarin fish is simply ... feeding. A 29 gallon aquarium simply does not support a manadrinfish based on the assumption that there are enough micro invertebrates for it to feed from. These fish can quickly wipe out large populations of micro inverts and in a large aquarium the invert population can replenish - in a small tank it simply cannot. If you want to keep a mandarinfish you will have to feed it. I have had the best luck with OVA. It's a fairly popular frozen food that is essentially prawn eggs and other nutrients. The issue often encountered is that mandarinfish are slow and methodical eaters. I place ova mixed with frozen mysis (both soaked in Garlic Power by Brightwell Aquatics and Zoe by Kent Marine) in a small glass jar at the bottom of my tank. The mandarin can swim in and eat and the food does not become disturbed by flow. The jar I use was $ 2 at the grocery store and is small enough that only the mandarin can get it. If you are willing to commit to feeding then a mandarin in a tank your size should work - if not I would say no.