I do think taking 1/3 of the media would cause a problem. Not to mention that the tank being seeded will still be very unstable (although better than not adding mature media). I think people need to get out of the habit of trying to cycle as fast as possible. If you don't have the patience to cycle a tank naturally, you don't have the patience for this hobby.
I’ve been doing this very thing for years, often slowing down with the fishroom during the summer, bringing it back up to capacity when the weather gets cold. I might have 15-20 tanks running during the summer, with plenty of extra sponge filters in each. I’d rather be outside in the sun with my dogs & my grill enjoying the summer.
Summer ends, I get breeding, maybe get in some new species, perhaps find a deal on a bulk purchase. I’ll take 1/3 of the media, usually a largish sponge filter, from a running stocked tank, fill an empty tank, and add fish as I see fit, by the stocking of the donor tank as well as the stocking of the newly filled tank. Light feeding on both for a week, along with a couple extra water changes that first week, not a problem. I can bring my room up to 30-35 tanks in a week that way if the situation demands. Tune in next spring, when I sell off stock, drain tanks, and double up filters in running tanks.
As a hobbyist I see no need to use mature media when starting a new tank, or cycling one over about 75 gallons. As a retailer I see no reason to change the filters I use for the rare occasion someone asks for mature media (otherwise you have to convice them to buy your gross, used media). As a service provider I see no reason to regularly use mature media. IME tanks run much better if you set them up properly and let them mature naturally. Trying to cut corners and rush things will only lead to complications. Not that using mature media is cutting corners, but trying to get the cycle to occur as quickly as possible is symptomatic of a larger issue of lack of patience. Even with mature media there is no guarantee of a tank cycling instantly or even signficantly faster.
I see no difference between what I do with anything from a 2.5 gallon hatching & fry tank up to 150 gallon tubs for growing fish out. The same principles apply, the scale is different. I could see a retailer not wanting to bother digging into what is often a centralized system for media that may be unsuitable for the most commonly found hobbyist filters, but would it be so hard to toss in a few common sizes of Aqua Clear sponges & bio wheels in with the bio balls of a sump? Banks of tanks & a sump, such as a Mars system, or many of other such site built retailer oriented systems could easily accommodate this, hopefully they would have a decent mechanical stage before their bio stage to eliminate a majority of the grossness.
I don’t see any of this as cutting corners or rushing, or a sign of anything other than having a good handle on the interaction between fish, stocking levels, and nitrifying bacterial levels. From experiences my handful of tanks is not an anomaly, being involved with two local clubs, knowing dozens of people with the same sort of setups give or take, and their doing the same thing with the same results leads me to believe that running extra bio filtration if you plan on having more tanks in the future is the best way to go. If you’re stuck in a pinch contact a local club, we do this sort of thing all the time.
Just because I'm no longer bothering to dive into fish shops to pick this week's top favourite fish doesn't mean that I'm going to give up on them by Christmas
/www.angelsplus.com/FiltersSponge.htm
