Hi Rusalka,
I'm in a similar situation. Now I have a quarantine tank, but it's too late, my fish got ich, in a NPT, and I have too many fish to put them in the quarantine tank, so I must treat the whole tank. Although external parasites are not treated with the same medications, I did a lot of research on people's experience with medication and plants/invertebrates (snails) and experienced some of it myself.
For reference, I have:
- 12 neons (all dead, got ich first)
- 7 lampeyes (killifish, were scratching)
- 2 wild blue rams (got white spots)
- 7 black phantom tetras (were scratching)
- 7 cory panda (one of the smallest cory species, were scratching )
- lots of pond/ramshorn snails. A few MTS.
Plants:
Duckweed
Moss ball
Crypt (walker I think)
Limnophila sessiliflora
Ludwigia repens
Hygrophilia polysperma
alternanthera reineckii
rotala indica
It's a 41 US gal.
Substrate: 1 inch of potting soil covered by 1/2 inch of gravel (it's a tall tank to the water compresses the substrate a lot).
First, for your internal parasites, I think that you can mix medication with food so it does not affect the whole tank (some of the medication leak, but not enough to harm the tank):
Garlic (it's not proven, but it worked for some people):
- You can chop a garlic clove, mix it with your food, put in the refrigerator for 30 minutes and then give it to your fish.
- You can use Seachem GarlicGuard or Kent Garlic Xtreme. I used Garlic Xtreme (it was supposed to help ich... did not really help, anyway). I found that my fish did not like flakes with garlic, but jumped on bloodworms with garlic.
Medicated gel/food:
e.g., Gel-Tek Ultra Cure PX (Praziquantel--0.0057%, Flubenol--0.03%, Metronidazole--0.3%): you don't feed your fish for a day, then you put some drops (follow the instruction) of the gel in the tank: the fish will "eat" the drops.
For future reference on ich treatment in a NPT, here is my experience:
-
I had a 9W UV sterilizer (50 gal/hr). Did not work.
-
I added a 24W UV sterilizer (113 gal/hr). Did not work. Kept the two sterilizers for the two next treatments. Btw, at this flow, I believe that they are supposed to kill free-swimming parasites...
-
I tried heat alone (32 C) for two weeks: it did not work. Fish stopped scratching, but my two blue rams still had white spots (less white spots, but still some). I think that there are some dead spots in the tank where the water was less warm. Also, I believe that my soil was less warm than 32 C. My hydor is a Hydor inline heater and after taking the temp readings at three different places, the temp was always 32 C so I don't know why it did not work... I put two large airstones in the tank.
Effect on plants: duckweed really did not like the heat. Other plants slowed their growth, but were still growing.
Effect on fish: the neons did not like it. Other fish were fine (no change in behavior, except that they breathed faster and the rams moved faster).
Effect on snails: they stopped reproducing

I saw a few empty shells at the bottom. No extermination though.
-
I tried heat (32C) and salt (1 1/2 teaspoon of salt per galon, added slowly over four days). Kept that for a week:
Got "rid" of the ich on one of the blue rams. The other ram kept getting reinfected. I saw one tetra scratching and two corys scratching. After a whole week.
Effect on plants: duckweed was almost dead. Alternanthera lost a few leaves. Same for crypt. But they kept growing.
Effect on fish: I lost all my neons (they became bloated, covered in white fluffy stuff and then with white spots). Cories became a bit bloated and were less energetic than usual. Other fish did not seem affected. I suspect that the salt stressed them and that's why they got reinfected. But all in all, this quantity of salt was not sufficient in killing the ich and I would not have felt safe to increase the salt.
Effect on snails: same as heat.
-
Seachem Paraguard (contains malachite green and aldehyde): I know that my ich is a strong strain, so I know it will probably take more than three days to get rid of it, no matter the medication (unless I want some of my fish dying in the process).
Before using it, I put carbon in my filter, did a few water changes to bring the salt back to 1 tbs/5 gallons and remove DOC. After three days, I turned off the UV, removed the carbon, brought down the temp to 28 C, and started using ParaGuard following the directions.
All fish stopped scratching after two days. Less white spots on the blue ram, but after a week, I saw a new one yesterday.
Effect on plants: nothing. The plants are happy and starting to get better because less salt and less heat. Paraguard does not seem to affect them.
Effect on fish: well, I guess that the water quality and conditions improved and made a big difference. The first two days, the cories did not like at all ParaGuard (they were again bloated and were swimming near the top). Now they are ok (they swim like their early days

).
Effect on snails: they started reproducing (I'm seeing eggs) for the better or the worse...
Summary:
- I know that some people got rid of ich more quickly and with gentler methods than the ones I used, so I'm not saying that UV, heat, heat and salt is not good. Maybe it would have worked if I had increased the salt of kept the treatment for longer, but I really felt that my tank ecology, as a whole, would have collapsed.
- ParaGuard seems to work and really does not hurt the plants or the snails. It does not color the water too

The reason I did not try a stronger medication is that I did not want to destroy my plants and kill a few hundreds snails dying at the same time in my tank. I will continue for another two weeks. If it does not work, I will probably have to use something harder (formalin and malachite green), siphon the inevitable empty snail shells and hope for the best for my plants and fish.
Those medications are hard to administer in a NPT because we have so much DOC that water change is, I think, a must for the medication to be effective.
- More importantly, I have a nano NPT with shrimps and we will introduce some lampeyes to keep them company. They are in the Q-Tank for a month as I write this post... I read about Q-Tank before but thought that I could be ok without them, despite the heavy and convincing literature on them. Oh, and my LFS says that they quarantine their fish. ah ah ah.
Hope this will help someone in the future,
Bart