what's a high tech tank and what's a low tech tank??

By my definition, high tech is high-powered fluorescent or LED lighting, injected CO2, and dry chemical fertilizer dosing using RO or RO/DI water. Basically, high-tech tanks would be a complete wreck without constant supervision and tinkering by their owners. For those like me who like to OCD over their tanks, I love it.

Low tech would be standard hood lighting, decent substrate, and fresh water, IMO. It's simple, low-maintenance, and effective. The limitations on what you can grow and keep are annoying though.

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Officially fishless until after the move....tune in later for details!

I personally think that high tech can be any planted tank with any level lighting, but using pressurized CO2 and dosing ferts. It really is a high enough level of lighting to actually require the other two. The light is the driving element. Using any special water would be a personal preference based off the water you have (tap) and can be for any tank.

From the point of view of a barbarian for whom plants are accessories to a tank, high tech can also be a drilled tank with plumbing and an outside sump and or a freshwater protein skimmer. It could have an automatic water changing system, in line heaters or ultraviolet, or any of the fun and expensive gadgets available to us.
Low tech would be hang on the back filters, or central air driven sponges or box filters. Depending on the fish, there could be a heater or not, and depending on the plants, lighting would come from a hardware store or from a standard hood.
Low-tech can be expensive in relative terms if the shop rips you off, but it is generally cheap and basic. High tech costs a lot more across the board. Low tech should be focused on the well-being of the fish, and not of the plants (which are necessary for the well being of fish from heavily vegetated habitats in nature).
There's a fellow on this forum who sells a build he's named after himself - with no filtration or water changes. It's a plant tank set up for easy plants, with fish secondary and not necessarily well off. If it's too low tech, it will take twice the work of a high tech tank if you want healthy and happy fish in there.
I'm a very low-tech, DIY type with homemade filters, cheap lights, a central air pump, etc. It works for me, but I'm in the minority.

Although some of what you list is technical, when people refer to high tech or low tech tanks it is the lighting, CO2 and ferts , if being used, they are referring to. It is more of a requirement driven tank and a term used by planted tank enthusiasts.

I'll respectfully disagree with jrman - i think if you are into planted tanks, the terms around 'tech' may be as Ben says. However, I often hear the 'high tech/low tech' terms thrown around in discussions of rapids fish tanks (plants are impossible there) or with tanks of messy herbivorous cichlids, where filtration technology has to be cutting edge.
You can pay hundred of dollars for state of the art computerized water pumps designed to make rapids fish feel very much at ease. I just read a manual for such a device, and trust me, it's high tech. It's a magnificent thing that borders on having a computer attached to your aquarium. I can't afford one, but the technology is really something.
We have hobbies within hobbies within hobbies in aquarium keeping, and the jargon crosses over. I personally would love to have a large tank with a high tech water pump, to see how rapids fish would live in something closer to approximating their habitat. Plants would not survive in such a set-up, although I would cultivate algae.
I'm new on this forum, and I've been really intrigued by the plant-keeping mainstream operating here - it is a very different aquarium-keeping culture than I'm used to. In my wing of the hobby, no one uses CO2 or worries about plants and lighting - but I know some serious technology geeks who engineer the habitats they keep fish in.
So I'd say high tech is when you need technology beyond what is found in the average aquarium kit in order to create a focused and planned aquarium set-up, either in terms of plant growth, attempted replication of habitats or the setting up of 'biotope' aquariums.
Every fish or plant has specialized needs you should know, but low-tech comes when you can met those needs using minimal equipment and technology. It works for fish and plants that come from easily replicated environments, or that easily adapt to aquarium life with no 'special needs'.

We're all entitled to an opinion. I don't think the stuff you refer to someone needs a definition of. It is not a "term" used, it is a tank with high tech features for sure. But, i can almost guarantee that the OP did not hear the term referring to some unusual filtration or something else out of the ordinary. Go to as little as 3-4 other sites of your choosing and most if not all, would agree with something similar to what I or Guy posted.

How should I know?

I just do what works.

but if you find yourself doing something after you did something, possibly you're on the way to high tech.

my .02

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fw leiden since 1979, fo salt since 1979, mixed reef 55g 2002-2009. Strong emphasis on the tank taking care of itself. Balanced with plant life, no water changes, tap water, no filters in FW. Only dosing calcium, alk, mag in marine reef tanks. http://www.aquariumforum.com/f15/my-...ods-26410.html
recent tanks (till 2009) 7 years- 10g FW leiden 7 yrs, 55g mixed reef 7, 2 yrs, 20g FW leiden, 10 g fw leiden , 29g mixed reef, current tank 55g leiden

Some work better than others.

Since the original poster wanted a definition of a term, I just wanted to add how I hear it used. I guess it could be regional - and since we have people from all over the world here, it never hurts to be on the same page. In all sincerity, I would never have called a planted tank with CO2 a high tech tank. In my corner of the world, that's 'planted' tank, and 'high tech' is usually reserved for filtration and expensive gadgets. A CO2 diffuser is just one of the more useful gadgets.

Either way, I'm a low tech DIY kind of fishkeeper - cheap equipment and low light plants. I have the greatest respect for those who have aquatic gardens in their tanks - they are things of beauty. What you guys are doing are 'high artistry' tanks, however we want to use the 'tech' phrase.