changing substrate and UGF

[dax29]

I've got a 29 gallon aquarium with an Aqualclear 200, a Tetra Whisper 30, and a [acronym:239e4071a7="Under Gravel Filter"]UGF[/acronym:239e4071a7] with no powerhead. I'm thinking of switching my colored gravel for a sand substrate b/c I have primarily loaches. All my loaches and other fish are 2" or less. I plan to use either playground sand or pool filter sand, with a few smooth, round brown pebbles mixed in.

My fish are as follows:
4 clown loaches
3 yo yo loaches
2 zebra loaches
2 angelicus loaches
2 SAEs
1 dwarf flame gourami (gonna go in a 10 gallon soon)

I'm at or over the limit of fish for my 29, but I plan to move them to a 75 gallon when they get bigger.

When I change out my gravel for sand (and ditch the [acronym:239e4071a7="Under Gravel Filter"]UGF[/acronym:239e4071a7]), can I save the old water in the tank and put it back in after I'm done changing and rearranging the tank? I don't want to start a new cycle. I have a 10 gallon [acronym:239e4071a7="quarantine or quart depending on context"]QT[/acronym:239e4071a7] the fish can hang out in while I'm doing this. The water parameters generally run identically between the two tanks unless I have the temp pumped up in the [acronym:239e4071a7="quarantine or quart depending on context"]QT[/acronym:239e4071a7] for ich. I plan on rinsing and cleaning the sand several times before I'm ready to do the switch. I'm also planning on putting in that little 100 [acronym:239e4071a7="Gallons per hour"]gph[/acronym:239e4071a7] Penquin Biowheel [acronym:239e4071a7="Hang On Back"]HOB[/acronym:239e4071a7] filter to offset the loss of the [acronym:239e4071a7="Under Gravel Filter"]UGF[/acronym:239e4071a7]. That, in addition to the Aqualclear 200 and the Whisper 30, will put me at 430 [acronym:239e4071a7="Gallons per hour"]gph[/acronym:239e4071a7] for the 29 gallon tank. That is overkill but it makes me feel like I'm doing all I can to keep the water in top shape. I already do 30% PWCs every 2-3 weeks as well.

Let me know if you think this is a good plan.

[cougaran]

When you lose the gravel you are going to lose a portion of the tanks ability to cycle the tank. But the nitrifying bacteria will still be present in the filter so dont change that. So if you take the fish out, empty most of the water into a clean trash barrel, remove the [acronym:8282e329ac="Under Gravel Filter"]ugf[/acronym:8282e329ac] & gravel, and put back sand then water it should be fine. I would wait at least two weeks before putting the fish back and chk the tank for ammonia, nitrite,and nitrate levels before putting the fish back. Be very careful with the clown loaches as they are ich magnets, so sudden changes in enviroments can stress them out.
Also in rereading your post you mention a you want to put in a penquin, i would set that up now and let the bacteria build up on it before the change. You will have more filtration than i ever had on my 29 [acronym:8282e329ac="Gallon"]gal[/acronym:8282e329ac], originally i had a whisper 3 and that was it.

[Fishyfanatic]

You don't have to wait before putting your fish back in the tank. When we switched from gravel to sand we put them back in the tank about 20 minutes after filling up the tank. If you notice a mini-cycle, just be prepared for water changes. With the amount of bacteria that you currently have in your filter, there shouldn't be a problem. Besides, if you leave them out of the tank for 2 weeks, you won't have any ammonia feeding the bacteria, thus it will die, needing to re-cycle the tank.

[dax29]

Thanks for the input so far. I will go ahead and get the mini Biowheel Penguin going in one of my other tanks so it will have some bacteria when I set up.

[cougaran]

I thought about that too, as no bioload for the nitrifying bacteria, but i figured if he put the old water in, it would still have enough ammonia to keep the filters nitrifying bacteria going for 2 weeks. But, Placing all the fish into the tank might be too much of a bioload for the tank, remember theres no gravel anymore.. A compromise might be just adding 1 or 2 fish to start to help get the tank cycling.
My concern is the clown loach, which just always seem to get ich at the drop of a hat. Maybe just leave them in the [acronym:7e56f5b662="quarantine or quart depending on context"]qt[/acronym:7e56f5b662] tank for a bit.

[Fishyfanatic]

No need to worry keeping the fish out of the tank. If you really want to be cautious, you could keep a couple in [acronym:bfa4db4f03="quarantine or quart depending on context"]QT[/acronym:bfa4db4f03], but its not necessary. I did the exact same thing with a 55 [acronym:bfa4db4f03="Gallon"]gal[/acronym:bfa4db4f03] tank full of African's (over stocked) and didn't incur any problems.

[dax29]

I've got 2 new Penguin 100 [acronym:a1f1a0f441="Gallons per hour"]gph[/acronym:a1f1a0f441] Bio-wheel filters running in my established [acronym:a1f1a0f441="quarantine or quart depending on context"]QT[/acronym:a1f1a0f441] so I can use them immediately when I set up a 10 gallon and when I add one to my 29. I'm running one of those in-tank 100 [acronym:a1f1a0f441="Gallons per hour"]gph[/acronym:a1f1a0f441] filters too which gives me 300 [acronym:a1f1a0f441="Gallons per hour"]gph[/acronym:a1f1a0f441] on that 10 gallon [acronym:a1f1a0f441="quarantine or quart depending on context"]QT[/acronym:a1f1a0f441]. I've only got 4 otos in there now. Is that enough to keep the tank cycling or should I add some fish to increase the bioload so I can get the bacteria population up on the 2 Penguins?

[BASSNMAN]

When I changed out a 55 gal to a 125, I saved the water and used the same filter but changed substrate. I put a bunch of the old gravel in a 2 gal plastic bucket and set it in the 125 and left it for 3 weeks. I added declor and finished filling with new water. I never had a recycle.