I think that you are doing your best for these fish and you are not under attack, and people are only trying to help you out. I know that it is hard to realize how we are saying the comments we type and post to the forum, but please try to hear them as being helpful and not hurtful.
I do not know how you can make a statement such as 'my fish are happy' or 'my fish like the lights' since obviously, they cannot tell you that. Granted there are some signs that point out to a fish being healthy, but not neccesarily happy. In nature, many bottom feeders or bottom dwellers are obviously secluded from a lot of light by the water above them. When these types of fish are put under the more intense lighting of an aquarium, then it can stress them. They can be stressed out without any visual signs to yourself and I admit, it does appear that your loaches look nice and healthy, but looks are not always what counts.
The filtration in your tank has some impact on if your fish live or die, but if you take it off, or even have too little filtration, the fish are most likely going to survive for a long while, but not to their full potential. I do not know what filtration you have exactly or how well it works in your tank and I also think that H3D is just making a general comment about filtration and not just picking on yours completely.
The thing I am trying to get across is that sometimes a grow out tank situation will not work for certain types of fish. Like I said, the small footprint, or the area in the bottom of your tank is very small compared to even the same gallon tank in the regular rectange shape. These loaches are usually active and full of energy and so it is generally best to keep them in a tank with more surface area in the bottom of your tank. Not having that room can stress them out, making them weaker and easier to get sick. The same would apply to keeping any very active fish in a small or short tank, not just the loaches. For example, most any schooling fish is going to want to swim back and forth. The other issue is that the fish in your tank cannot be as confident being out in the open knowing that they have very limited room to run. The same is especially true for fish that grow long rather than round because they need more room in a tank to turn around. Eventually, if you were going to keep these loaches in your tank, you would have the same issue.
Finally, having 6 clown loaches in your tank is just too many, IMO and experience. This is because the clown loach is a micro-eater, meaning that it will only eat very small amounts at a time, but on a more frequent basis. So, without wanting to over feed, it is going to be hard for you to keep a good, steady supply of food on the substrate of your tank for 6 loaches. This is what they are doing when they are foraging around the tank. You can always notice a problem in your tank if your bottom feeders like clown loaches can often be seen swimming up into the upper areas of the tank. This is a sign that they are not finding enough food at the bottom and want to look elsewhere.
These are all just my opinons and I can feel ok about that. However, they are informed opinions and I have kept clown loaches myself. It is not you who I am worried about, just your fish because I would like to see you keep them for a very long time. I also realize that this is the picture thread and I have already been told that it isn't the best place to bring up topics like this one and so I do not want to keep moving further and further away from that.