Rock caves/decor from foam and concrete?
Ive wanted something taller/bigger to split my tank up a bit more for my mbuna cichlids, but could never find anything tall enough. I have around 16 of those "Underwater Galleries cichlid stones" which i think are great, but pricey. I like that they dont displace really any water like real rocks, and theyre very light so i dont have to worry so much about falling. So instead of buying another large pack of those, i was thinking of doing something like the rock backgrounds ive seen people make but instead make a mountain. I would like to displace as little water as possible, and create as many caves/hallways for the fish to occupy as well. I beleive my tank is 21" tall (75 gallon), so im hoping to reach more towards the top to split the tank more into two sides for territories.
Any ideas? Maybe first i should ask how it is done without posing any risk to the fish?