snails can be pretty illusive sometimes - they are fascinating creatures to observe.
have you ever fed them zucchini? my apple snails love it. I attach a slice to a veggie clip and place it low in the tank. Some times I'll see 2 of them hanging on it - one on either side, just munching away.
If you try it, it may take them a while to find it. make sure you replace the slice at least every other day and sink a new one in the same place so they know where to look for it. Between my bristle nose pleco and the 3 snails, they go through a round every day :o)
30 g FW planted:corys, ABNP, blue angel, harleys, zebra danios, nerites & mystery snails
15 g FW planted: crown tail betta, neons, snails
90 g FW semi planted: Blood Parrots, severum, Jurupari, EBJD, congos, kribs, clown pleco, snails
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Fishless cycling: http://www.aquaticcommunity.com/aqua...ead.php?t=5640
Cycling with fish: http://www.aquaticcommunity.com/aqua...ad.php?t=36492