Originally Posted by Pufferfish22
I have a 150 litre tropical set up, currently home to 5 harlequin rasboras, 3 neon tetras (not going to increase these as my water doesn't seem to suit them and I've never managed to successfully keep them) 3 redline tetras (same as neons?) 5 cory's and 2 snails. My water here is hard and does contain naturally high levels of nitrate as we are a rural farming area. I'd like something that is eye catching and good on the eye and not aggressive. What can you suggest?
As Byron mentioned, quantifying the hardness and pH would be helpful. Neon Tetra are more in the soft water direction, according to the profile here so if your water is hard enough it could affect them negatively. Also, they are a shoaling fish so having them in a group of less than six might also add to their problems.
I assume that you are on a well based on your nitrates being affected by the farming in the area and that your water may be on the high side of hard... close to 20dGH. Our water was over this, without the nitrates, so I looked into hard water fish that were not live bearers, (some will suggest something along that line but I have not looked at them at all, personal preference only).
My list ended up with Bloodfin Tetra, Black Widow Tetra, Flame Tetra, Pristella Tetra, and Cherry Barb. We ended up with a dozen Cherry Barbs. These would all be suitable for a 40 gallon tank. The barbs are a better choice for a community tank given our particulars but the others, due diligence applied, should be good choices for you also.