- Tests have gotten back to normal after cleaning the gravel, doing a partial water change and cycling it for 2 weeks
Kinda wish I had found this thread earlier to give you some more tips. You should always cycle your tank for 3-4 weeks before adding fish at all.
- Underwater plants have started growing roots. Is gravel okay to grow plants if there are root tabs or do I need to add a layer of aquasoil? If so, what is the best brand (cost-effective)
If you want to add aquasoil, it would be better to get it under the gravel. So you'd essentially have to re-do the whole tank. If you do want to re-do the tank I suggest doing it like this, as it creates a really healthy tank:
- Use a mix of large and small gravel as a bottom layer. This provides some structure to the bottom of the tank and creates a home for beneficial bacteria and micro-organisms, helping filtration.
- Grab a small bucket of scum and mud from a healthy creek or pond, this introduces micro-organisms that should be a huge help with keeping the tank clean and healthy. Use this as the second layer of the tank.
- Use a tub of aquasoil as a third layer, this will probably be the largest layer. I also suggest creating a small hill in the back of the tank. I'm not familiar with American brands, so I can't recommend a specific one.
- Add hardscape (rocks, driftwood and any other decoration, I suggest getting some wood in there) and then plants. The amazon swords should be partially dug into the aquasoil, and the Java fern attached to the rocks or wood (as someone already mentioned). Personally, I'd also get a few more plants, especially in the back of the tank. The dwarf clawed frogs would especially appreciate it.
- Finally add the gravel as the top layer to keep it all in place.
- Add water slowly. I usually do a mixture of creek water, rain water and tap water. But I have access to a local creek and very clean tap water, so that depends on your situation.
- I also add some leaf litter to my tank every now and then, and they do gradually disappear by being eaten by the micro-organisms.
-I'm not likely going to get some new inhabitants until March but my plan is to get the following species:
- A group of snails and shrimps to help clean the tank along with a small group of catfish (Cory?)
- A small school of congo tetra
- A couple more guppies
Quite frankly, your tank is pretty small and overstocking could quickly be an issue. I suggest Dwarf otocinclus and pagoda snails (pagoda because they eat algae and don't breed or lay eggs too fast. Nerites lay eggs that won't hatch EVERYWHERE) as a cleanup crew. Amano shrimp are also good for clearing up food scraps, but I don't know how they play with Dwarf clawed frogs.
A school of Congo tetras, even a small one, would probably be too large for this tank. Especially in the current state. Small rasboras like Harlequin would probably be fine, but having just a group of guppies in this tank as shoalers would probably fill it up enough.
- I got a Home Depot 5-gallon bucket and a small 5-gallon sponge filter. If I get a heater, would it be okay if this would be a cost-effective quarantine tank?
A bucket should be fine for a quarantine, but I would add simple hides and a bubbler to reduce stress