Rosy Barbs are cool water fish, optimum temperature in the low 70s.
Clown Loaches are warm water fish, thriving in the uppermost 70s to 80*. Not good tank mates.
I keep fish in the Q-tank for a month PLUS medication time. So if I see some Ich, I treat it, then re-start the calendar for another month.
Good that you know ahead of time what the new water will be like!
Here is how I would do this:
Get some reverse osmosis or distilled water (Grocery store, fish store...) and make water changes with this water. This will slowly soften the water in the tanks over the next month or so before you move.
After you move you may have to add some minerals to the new water if the fish are not yet fully acclimated to the softer water. Let it take time. It is harder on the fish to move into softer water. It takes their body several weeks or a month to adjust, and it cannot be rushed.
Use the GH test as your guide. About twice a week do a water change, and the new GH once the water change is done will be about 1 German degree of hardness lower than it was before the water change.
If you have a TDS meter, then the new TDS might be 8-10% lower than it was before.
Here is how that might work:
Lets say your current GH is 16 degrees, TDS 800 ppm.
You want to do a 25% water change.
Make up the new water as a blend of tap and distilled (or RO) that the GH is 12 degrees, TDS 600 ppm . When you add this water to the tank the resulting GH will be 15 degrees, the TDS 750 ppm.
Here is how the math works:
You are removing 25% of the water from the tank and replacing it.
To figure the water chemistry use this formula:
.........75% of the GH of the tank water ( .75 x 16 = 12)
Plus 25% of the GH of the new water (.25 x 12 = 3)
equals the net GH when the water is mixed. (12 + 3 = 15)
Same formula for the TDS:
.........75% of the TDS of the tank water (.75 x 800 = 600)
plus 25% of the TDS of the new water (.25 x 600 = 150)
equals the net TDS of the water when they are mixed. (600 + 150 = 750)
Test: 10% of 800 ppm is 80 ppm. 800 - 80 = 720 ppm. New water should not be softer than this for the first water change. 750 ppm is OK.
Altering the GH 1 degree lower twice a week is a conservative, safe change. It may be possible to move faster than this, for example doing more water changes, but do not make a greater change in any one water change. I have had problems with fish when the TDS is lowered by more than 10% at one time, or more frequently than twice a week.
If the 25% twice a week does not keep the nitrates really low then do more water changes, but match the GH of the new water to the water in the tank so there is not too big a change.
Moving with fish:
A) Ahead of time:
1) Do some extra water changes that emphasize gravel vacuuming. Really work to get the gravel clean.
2) Clean the filter several days or a week ahead of time.
3) Get together the things you will need.
B) Day of the move:
1) Siphon clean water into several buckets.
2) Put fish into buckets: Separate species in each bucket, aggressive fish get a separate bucket, Loaches get a separate bucket. About 2 gallons of water and up to 6-8 small fish like Tetras or 1 larger fish per bucket. Stress Coat is a good product for helping in a situation like this. Cover the buckets. Fish jump. Keep the buckets at the same temperature, do not allow them to get chilled or over heated.
3) Siphon more water into more buckets for plants.
4) Use more buckets for substrate, and buckets for filter media. If it will only be half an hour the nitrifying bacteria will be fine in the filter, just drain most of the water. Damp is fine for the bacteria. If it will be longer than half an hour then put the filter media in a bucket with enough water to keep the humidity up. Does not have to be covered in water. These bacteria need oxygen.
5) Move the tanks with help. They are heavy, and twisting them can break open the silicone, starting a leak. Keep them well supported when you move them. Blanket or cardboard can protect them from scratches, especially an acrylic tank.
C) Arrival:
1) Get water ready. I use a Rubbermaid Brute garbage can. Test the new water. If the GH is lower than the GH of the tank water then add Seachem Equilibrium to raise the GH until it matches. This material does not dissolve very well, so start this mix right away, and do not add very much Equilibrium. I use a small pump to keep the water moving until it is all dissolved. Test, then add more if needed. Don't forget dechlor! (It helps to shake up the Equilibrium in a jar of hot water to help it dissolve faster) While the water is circulating, go on to the next few steps, then return and test and adjust the recipe.
2) Set up stand and tank, make sure it is level. (Test the water in the garbage can again, adjust...)
3) Put the substrate in the tank, and arrange driftwood, rocks and ceramic castles. (Test the water in the garbage can again, adjust...)
4) Add enough water to not quite cover the substrate. Pour it in slowly, using a plate or plastic bag so the water does not hit the substrate and stir it up. (This is not much water. Use the water you have prepared, even if you are still adjusting the recipe.)
5) Plant, misting the plants a lot.
6) Add more water. You can use water that you brought with you in the various buckets, but not the fish buckets. Use a plate or plastic bag again so the substrate is not disturbed. Pour the water in slowly. Test the GH. If it is as much as 1 degree lower or 2 degrees higher than the tank water was at the other house this is OK, not too much of a change for the fish. If the GH is still too soft, add some Epsom salt or more Seachem Equilibrium. If it is too hard then add more soft tap water.
7) Set up and check that the equipment is working.
A good addition at this point is a small bottle of Tetra Safe Start or Dr. Tim's One and Only. These products contain the nitrifying bacteria that you are working so hard to save. They are added insurance that the newly set up system will have enough bacteria to deal with the extra ammonia that is commonly produced by stressed fish for the next several hours.
Add fish by netting them out of the buckets. Do not put the water from the fish buckets in the tank. Stressed fish produce more ammonia than average, and stress hormones. Some Loaches seem to produce a toxin in their slime coat that can kill the other fish. You do not want this water going into the new tank!
D) The rest of the day:
1) Lights out.
2) If the room is busy hang a towel or blanket over the front of the tank so the fish will not be so scared. Dark is less stressful for the fish.
3) Do not feed.
4) Monitor the temperature and equipment to be sure it is working.
E) The next day:
1) Test the water for ammonia and nitrite. Be ready to do a water change, make sure the GH matches.
2) Feed about half of normal
3) Lights on if you have live plants. If the fish are still unsettled, it is OK to leave the lights off today, or only turn them on just when you feed.
F) the rest of the week:
Regular feeding, regular light schedule.
Keep monitoring ammonia, nitrite and nitrate. Do water changes as needed. Do not worry about dropping the GH yet. If it is still higher than the tap water just add some Equilibrium to make it the same as what the fish are used to.
G) After the first week:
Now go ahead and continue dropping the GH until the fish are living in the new tap water with no minerals added. Remember to drop the GH no more than 1 degree per water change, and you can do 2 water changes per week with this sort of change. If the tank needs more water changes then do them without dropping the GH.
38 tanks, 2 ponds over 4000 liters of water to keep clean and fresh.
Happy fish keeping!
