You can answer your own question by posting a full tank shot of your 600G. It's only going to get worse as the Albino Pacu (3 of 'em?), Wels Catfish and 12+ GATFs continue to grow...that is if they live long enough. The crazy part is that's just the tip of the iceberg...you have many more fish that will outgrow all of your tanks.
The gist of what I am saying is that if you plan a tank with the full or even the expected average size of a fish in mind and keep the number of fish within reason, you will have much greater success. You won't have to do 80% water changes 3 times a week just to keep your Nitrate levels below lethal or at the very least harmful levels. I know you will be offended by my advice...after all, you are a "pro." But I guarantee you would have much fewer losses if you thin out your coin collection.
If you continue down the same path I guarantee the pile of dead fish will continue to grow. I don't care if I don't convince you, but I know there are some noobies that are taking the time to read this thread that are starting to think for themselves...maybe there is a better way to keep fish...maybe instead of spending all their money on obtaining exotic species, you should invest as much if not more into an appropriate environment for them to live?
A few people have mentioned PETA and how they are concerned that the organization is going to ban fishkeeping alltogether. I guess it makes sense that some of the people most afraid of PETA are the same people giving the organization ammunition to put an end to our hobby. When you set out with the frame of mind that you are going to hoard as many huge fish as possible regardless of any tank size limitations, it reflects poorly on all of us. When you base your stocking decisions on your own impulsive desires without thinking and planning for the fishes future needs, you are being selfish and unethical. It's the MFKers with massively overstocked tanks, pix of fish that have torn each other to shreds due to the owners ignorance/incompetence that make us all look bad.
If more people had setups that looked like Jose's, you think PETA would be able to garner any support to put an end to our hobby? Again, I'm not against keeping monster fish and I'm not suggesting everyone should only keep discus or little tetras. All I am suggesting is to be practical and use good judgment. That should not be controversial, but for whatever reason it is.
Another long post, and you still came up empty, no information. So, after claiming that I'm king of cramming big fish in small tank, accusing me of hoarding as many huge fish as possible regardless of any tank size limitations, reflects poorly on all of us, base my stocking decision on my own impulsive desires without thinking and planning the fish future needs, being selfish and unethical, you want me to post a full tank shots of my 600gal? Which 600gal full tank shot do you want me to post? Do you know how many 600gal tanks or how many tanks and their size do I have?
I thought you would learn something, after the trip to Steinhart aquarium, but you still don't. Didn't you said and I quote, "In other words, even the pros do frequent water changes...in order to keep fish healthy, there's no way around it?" And here, you think if I do so and so, I won't have to do 80% water changes 3 times a week just to keep your Nitrate levels below lethal or at the very least harmful levels? I don't know why you even bother to bring Jose setups into the conversation, but even Jose is still struggling to keep his discus survive.
Whether you care or not, you can't convince me when you just pass out second-hand information. A parrot can do that. You can't expect to help the hobby by sitting there and waiting for others to spoonfed you information so that you can put your setup together thru an easy and cheap route. You got to learn. You may look good, well talk, but just like your tank or your sump, look good and clean, but empty and poor design. Seriously, that sump with all those bio-ball floating around, and those heaters laying there reflects poorly on all of us. With thousands of members, a DIY forum, and you still put a sump together like that is unbelievable! At least, read and follow the instruction from the manufacturer.
